diff --git a/app/controllers/admin/instances/moderation_notes_controller.rb b/app/controllers/admin/instances/moderation_notes_controller.rb
new file mode 100644
index 000000000..635c09734
--- /dev/null
+++ b/app/controllers/admin/instances/moderation_notes_controller.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+class Admin::Instances::ModerationNotesController < Admin::BaseController
+  before_action :set_instance, only: [:create]
+  before_action :set_instance_note, only: [:destroy]
+
+  def create
+    authorize :instance_moderation_note, :create?
+
+    @instance_moderation_note = current_account.instance_moderation_notes.new(content: resource_params[:content], domain: @instance.domain)
+
+    if @instance_moderation_note.save
+      redirect_to admin_instance_path(@instance.domain, anchor: helpers.dom_id(@instance_moderation_note)), notice: I18n.t('admin.instances.moderation_notes.created_msg')
+    else
+      @instance_moderation_notes = @instance.moderation_notes.includes(:account).chronological
+      @time_period = (6.days.ago.to_date...Time.now.utc.to_date)
+      @action_logs = Admin::ActionLogFilter.new(target_domain: @instance.domain).results.limit(5)
+
+      render 'admin/instances/show'
+    end
+  end
+
+  def destroy
+    authorize @instance_moderation_note, :destroy?
+    @instance_moderation_note.destroy!
+    redirect_to admin_instance_path(@instance_moderation_note.domain, anchor: 'instance-notes'), notice: I18n.t('admin.instances.moderation_notes.destroyed_msg')
+  end
+
+  private
+
+  def resource_params
+    params
+      .expect(instance_moderation_note: [:content])
+  end
+
+  def set_instance
+    domain = params[:instance_id]&.strip
+    @instance = Instance.find_or_initialize_by(domain: TagManager.instance.normalize_domain(domain))
+  end
+
+  def set_instance_note
+    @instance_moderation_note = InstanceModerationNote.find(params[:id])
+  end
+end
diff --git a/app/controllers/admin/instances_controller.rb b/app/controllers/admin/instances_controller.rb
index a48c4773e..6ab4acab9 100644
--- a/app/controllers/admin/instances_controller.rb
+++ b/app/controllers/admin/instances_controller.rb
@@ -14,6 +14,9 @@ module Admin
 
     def show
       authorize :instance, :show?
+
+      @instance_moderation_note = @instance.moderation_notes.new
+      @instance_moderation_notes = @instance.moderation_notes.includes(:account).chronological
       @time_period = (6.days.ago.to_date...Time.now.utc.to_date)
       @action_logs = Admin::ActionLogFilter.new(target_domain: @instance.domain).results.limit(LOGS_LIMIT)
     end
@@ -52,7 +55,8 @@ module Admin
     private
 
     def set_instance
-      @instance = Instance.find_or_initialize_by(domain: TagManager.instance.normalize_domain(params[:id]&.strip))
+      domain = params[:id]&.strip
+      @instance = Instance.find_or_initialize_by(domain: TagManager.instance.normalize_domain(domain))
     end
 
     def set_instances
diff --git a/app/javascript/styles/mastodon/admin.scss b/app/javascript/styles/mastodon/admin.scss
index bc51163f1..3709a4f50 100644
--- a/app/javascript/styles/mastodon/admin.scss
+++ b/app/javascript/styles/mastodon/admin.scss
@@ -1632,6 +1632,17 @@ a.sparkline {
         }
       }
 
+      a.timestamp {
+        color: $darker-text-color;
+        text-decoration: none;
+
+        &:hover,
+        &:focus,
+        &:active {
+          text-decoration: underline;
+        }
+      }
+
       time {
         margin-inline-start: 5px;
         vertical-align: baseline;
diff --git a/app/models/concerns/account/associations.rb b/app/models/concerns/account/associations.rb
index cafb2d151..62c55da5d 100644
--- a/app/models/concerns/account/associations.rb
+++ b/app/models/concerns/account/associations.rb
@@ -18,6 +18,7 @@ module Account::Associations
         has_many :favourites
         has_many :featured_tags, -> { includes(:tag) }
         has_many :list_accounts
+        has_many :instance_moderation_notes
         has_many :media_attachments
         has_many :mentions
         has_many :migrations, class_name: 'AccountMigration'
diff --git a/app/models/instance.rb b/app/models/instance.rb
index 3bd4b924a..01d258281 100644
--- a/app/models/instance.rb
+++ b/app/models/instance.rb
@@ -21,6 +21,7 @@ class Instance < ApplicationRecord
     belongs_to :unavailable_domain
 
     has_many :accounts, dependent: nil
+    has_many :moderation_notes, class_name: 'InstanceModerationNote', dependent: :destroy
   end
 
   scope :searchable, -> { where.not(domain: DomainBlock.select(:domain)) }
diff --git a/app/models/instance_moderation_note.rb b/app/models/instance_moderation_note.rb
new file mode 100644
index 000000000..fedb571fb
--- /dev/null
+++ b/app/models/instance_moderation_note.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: instance_moderation_notes
+#
+#  id         :bigint(8)        not null, primary key
+#  content    :text
+#  domain     :string           not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  account_id :bigint(8)        not null
+#
+class InstanceModerationNote < ApplicationRecord
+  include DomainNormalizable
+  include DomainMaterializable
+
+  CONTENT_SIZE_LIMIT = 2_000
+
+  belongs_to :account
+  belongs_to :instance, inverse_of: :moderation_notes, foreign_key: :domain, primary_key: :domain, optional: true
+
+  scope :chronological, -> { reorder(id: :asc) }
+
+  validates :content, presence: true, length: { maximum: CONTENT_SIZE_LIMIT }
+  validates :domain, presence: true, domain: true
+end
diff --git a/app/policies/instance_moderation_note_policy.rb b/app/policies/instance_moderation_note_policy.rb
new file mode 100644
index 000000000..f99a25fb5
--- /dev/null
+++ b/app/policies/instance_moderation_note_policy.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class InstanceModerationNotePolicy < ApplicationPolicy
+  def create?
+    role.can?(:manage_federation)
+  end
+
+  def destroy?
+    owner? || (role.can?(:manage_federation) && role.overrides?(record.account.user_role))
+  end
+
+  private
+
+  def owner?
+    record.account_id == current_account&.id
+  end
+end
diff --git a/app/views/admin/instances/show.html.haml b/app/views/admin/instances/show.html.haml
index 812a9c887..c977011e1 100644
--- a/app/views/admin/instances/show.html.haml
+++ b/app/views/admin/instances/show.html.haml
@@ -6,7 +6,7 @@
     = date_range(@time_period)
 
   - if @instance.persisted?
-    = render 'dashboard', instance_domain: @instance.domain, period_end_at: @time_period.last, period_start_at: @time_period.first
+    = render 'admin/instances/dashboard', instance_domain: @instance.domain, period_end_at: @time_period.last, period_start_at: @time_period.first
   - else
     %p
       = t('admin.instances.unknown_instance')
@@ -55,6 +55,24 @@
       = render partial: 'admin/action_logs/action_log', collection: @action_logs
     = link_to t('admin.instances.audit_log.view_all'), admin_action_logs_path(target_domain: @instance.domain), class: 'button'
 
+%hr.spacer/
+
+- if @instance.domain.present?
+  %h3#instance-notes= t('admin.instances.moderation_notes.title')
+  %p= t('admin.instances.moderation_notes.description_html')
+  .report-notes
+    = render partial: 'admin/report_notes/report_note', collection: @instance_moderation_notes
+
+  = simple_form_for @instance_moderation_note, url: admin_instance_moderation_notes_path(instance_id: @instance.domain) do |form|
+    = render 'shared/error_messages', object: @instance_moderation_note
+
+    .field-group
+      = form.input :content, input_html: { placeholder: t('admin.instances.moderation_notes.placeholder'), maxlength: InstanceModerationNote::CONTENT_SIZE_LIMIT, rows: 6, autofocus: @instance_moderation_note.errors.any? }
+
+    .actions
+      = form.button :button, t('admin.instances.moderation_notes.create'), type: :submit
+
+- if @instance.persisted?
   %hr.spacer/
 
   %h3= t('admin.instances.availability.title')
diff --git a/app/views/admin/report_notes/_report_note.html.haml b/app/views/admin/report_notes/_report_note.html.haml
index 9c8e267d6..7a51fdab2 100644
--- a/app/views/admin/report_notes/_report_note.html.haml
+++ b/app/views/admin/report_notes/_report_note.html.haml
@@ -1,11 +1,12 @@
-.report-notes__item
+.report-notes__item{ id: dom_id(report_note) }
   = image_tag report_note.account.avatar.url, class: 'report-notes__item__avatar'
 
   .report-notes__item__header
     %span.username
       = link_to report_note.account.username, admin_account_path(report_note.account_id)
-    %time.relative-formatted{ datetime: report_note.created_at.iso8601, title: report_note.created_at }
-      = l report_note.created_at.to_date
+    %a.timestamp{ href: "##{dom_id(report_note)}" }
+      %time.relative-formatted{ datetime: report_note.created_at.iso8601, title: report_note.created_at }
+        = l report_note.created_at.to_date
 
   .report-notes__item__content
     = linkify(report_note.content)
@@ -14,5 +15,7 @@
     .report-notes__item__actions
       - if report_note.is_a?(AccountModerationNote)
         = table_link_to 'delete', t('admin.reports.notes.delete'), admin_account_moderation_note_path(report_note), method: :delete
+      - elsif report_note.is_a?(InstanceModerationNote)
+        = table_link_to 'delete', t('admin.reports.notes.delete'), admin_instance_moderation_note_path(instance_id: report_note.domain, id: report_note.id), method: :delete
       - else
         = table_link_to 'delete', t('admin.reports.notes.delete'), admin_report_note_path(report_note), method: :delete
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 5fcdbe4c9..6633ffa4a 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -578,6 +578,13 @@ en:
         all: All
         limited: Limited
         title: Moderation
+      moderation_notes:
+        create: Add Moderation Note
+        created_msg: Instance moderation note successfully created!
+        description_html: View and leave notes for other moderators and your future self
+        destroyed_msg: Instance moderation note successfully deleted!
+        placeholder: Information about this instance, actions taken, or anything else that will help you moderate this instance in the future.
+        title: Moderation Notes
       private_comment: Private comment
       public_comment: Public comment
       purge: Purge
diff --git a/config/routes/admin.rb b/config/routes/admin.rb
index e7439f66b..3d9f24ae8 100644
--- a/config/routes/admin.rb
+++ b/config/routes/admin.rb
@@ -91,6 +91,8 @@ namespace :admin do
       post :restart_delivery
       post :stop_delivery
     end
+
+    resources :moderation_notes, controller: 'instances/moderation_notes', only: [:create, :destroy]
   end
 
   resources :rules, only: [:index, :new, :create, :edit, :update, :destroy] do
diff --git a/db/migrate/20250328153843_create_instance_moderation_notes.rb b/db/migrate/20250328153843_create_instance_moderation_notes.rb
new file mode 100644
index 000000000..eff0ad3bd
--- /dev/null
+++ b/db/migrate/20250328153843_create_instance_moderation_notes.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class CreateInstanceModerationNotes < ActiveRecord::Migration[8.0]
+  def change
+    create_table :instance_moderation_notes do |t|
+      t.string :domain, null: false
+      t.belongs_to :account, foreign_key: { on_delete: :cascade }, index: false, null: false
+      t.text :content
+
+      t.timestamps
+
+      t.index ['domain'], name: 'index_instance_moderation_notes_on_domain'
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index b7a8154f9..1064d8862 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -191,8 +191,8 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_05_110215) do
     t.boolean "hide_collections"
     t.integer "avatar_storage_schema_version"
     t.integer "header_storage_schema_version"
-    t.datetime "sensitized_at", precision: nil
     t.integer "suspension_origin"
+    t.datetime "sensitized_at", precision: nil
     t.boolean "trendable"
     t.datetime "reviewed_at", precision: nil
     t.datetime "requested_review_at", precision: nil
@@ -580,6 +580,15 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_05_110215) do
     t.index ["user_id"], name: "index_identities_on_user_id"
   end
 
+  create_table "instance_moderation_notes", force: :cascade do |t|
+    t.string "domain", null: false
+    t.bigint "account_id", null: false
+    t.text "content"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["domain"], name: "index_instance_moderation_notes_on_domain"
+  end
+
   create_table "invites", force: :cascade do |t|
     t.bigint "user_id", null: false
     t.string "code", default: "", null: false
@@ -595,12 +604,12 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_05_110215) do
   end
 
   create_table "ip_blocks", force: :cascade do |t|
-    t.inet "ip", default: "0.0.0.0", null: false
-    t.integer "severity", default: 0, null: false
-    t.datetime "expires_at", precision: nil
-    t.text "comment", default: "", null: false
     t.datetime "created_at", precision: nil, null: false
     t.datetime "updated_at", precision: nil, null: false
+    t.datetime "expires_at", precision: nil
+    t.inet "ip", default: "0.0.0.0", null: false
+    t.integer "severity", default: 0, null: false
+    t.text "comment", default: "", null: false
     t.index ["ip"], name: "index_ip_blocks_on_ip", unique: true
   end
 
@@ -1372,6 +1381,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_05_110215) do
   add_foreign_key "follows", "accounts", name: "fk_32ed1b5560", on_delete: :cascade
   add_foreign_key "generated_annual_reports", "accounts"
   add_foreign_key "identities", "users", name: "fk_bea040f377", on_delete: :cascade
+  add_foreign_key "instance_moderation_notes", "accounts", on_delete: :cascade
   add_foreign_key "invites", "users", on_delete: :cascade
   add_foreign_key "list_accounts", "accounts", on_delete: :cascade
   add_foreign_key "list_accounts", "follow_requests", on_delete: :cascade
diff --git a/spec/fabricators/instance_moderation_note_fabricator.rb b/spec/fabricators/instance_moderation_note_fabricator.rb
new file mode 100644
index 000000000..6a8fd3dc6
--- /dev/null
+++ b/spec/fabricators/instance_moderation_note_fabricator.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+Fabricator(:instance_moderation_note) do
+  domain { sequence(:domain) { |i| "#{i}#{Faker::Internet.domain_name}" } }
+  account { Fabricate.build(:account) }
+  content { Faker::Lorem.sentence }
+end
diff --git a/spec/models/instance_moderation_note_spec.rb b/spec/models/instance_moderation_note_spec.rb
new file mode 100644
index 000000000..4d77d4971
--- /dev/null
+++ b/spec/models/instance_moderation_note_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe InstanceModerationNote do
+  describe 'chronological' do
+    it 'returns the instance notes sorted by oldest first' do
+      instance = Instance.find_or_initialize_by(domain: TagManager.instance.normalize_domain('mastodon.example'))
+
+      note1 = Fabricate(:instance_moderation_note, domain: instance.domain)
+      note2 = Fabricate(:instance_moderation_note, domain: instance.domain)
+
+      expect(instance.moderation_notes.chronological).to eq [note1, note2]
+    end
+  end
+
+  describe 'validations' do
+    it 'is invalid if the content is empty' do
+      note = Fabricate.build(:instance_moderation_note, domain: 'mastodon.example', content: '')
+      expect(note.valid?).to be false
+    end
+
+    it 'is invalid if content is longer than character limit' do
+      note = Fabricate.build(:instance_moderation_note, domain: 'mastodon.example', content: comment_over_limit)
+      expect(note.valid?).to be false
+    end
+
+    it 'is valid even if the instance does not exist yet' do
+      note = Fabricate.build(:instance_moderation_note, domain: 'non-existent.example', content: 'test comment')
+      expect(note.valid?).to be true
+    end
+
+    def comment_over_limit
+      Faker::Lorem.paragraph_by_chars(number: described_class::CONTENT_SIZE_LIMIT * 2)
+    end
+  end
+end
diff --git a/spec/models/instance_spec.rb b/spec/models/instance_spec.rb
index 3e811d332..f1035816d 100644
--- a/spec/models/instance_spec.rb
+++ b/spec/models/instance_spec.rb
@@ -3,9 +3,9 @@
 require 'rails_helper'
 
 RSpec.describe Instance do
-  describe 'Scopes' do
-    before { described_class.refresh }
+  before { described_class.refresh }
 
+  describe 'Scopes' do
     describe '#searchable' do
       let(:expected_domain) { 'host.example' }
       let(:blocked_domain) { 'other.example' }
diff --git a/spec/requests/admin/instances/moderation_notes_spec.rb b/spec/requests/admin/instances/moderation_notes_spec.rb
new file mode 100644
index 000000000..18c9464bb
--- /dev/null
+++ b/spec/requests/admin/instances/moderation_notes_spec.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin Report Notes' do
+  describe 'POST /admin/instance/moderation_notes' do
+    before { sign_in Fabricate(:admin_user) }
+
+    it 'gracefully handles invalid nested params' do
+      post admin_instance_moderation_notes_path(instance_id: 'mastodon.test', instance_note: 'invalid')
+
+      expect(response)
+        .to have_http_status(400)
+    end
+  end
+end
diff --git a/spec/requests/admin/instances_spec.rb b/spec/requests/admin/instances_spec.rb
index afb6602a2..651f0bb6c 100644
--- a/spec/requests/admin/instances_spec.rb
+++ b/spec/requests/admin/instances_spec.rb
@@ -4,9 +4,9 @@ require 'rails_helper'
 
 RSpec.describe 'Admin Instances' do
   describe 'GET /admin/instances/:id' do
-    context 'with an unknown domain' do
-      before { sign_in Fabricate(:admin_user) }
+    before { sign_in Fabricate(:admin_user) }
 
+    context 'with an unknown domain' do
       it 'returns http success' do
         get admin_instance_path(id: 'unknown.example')
 
@@ -14,5 +14,14 @@ RSpec.describe 'Admin Instances' do
           .to have_http_status(200)
       end
     end
+
+    context 'with an invalid domain' do
+      it 'returns http success' do
+        get admin_instance_path(id: ' ')
+
+        expect(response)
+          .to have_http_status(200)
+      end
+    end
   end
 end
diff --git a/spec/system/admin/account_moderation_notes_spec.rb b/spec/system/admin/account_moderation_notes_spec.rb
index fa930cea2..728d17147 100644
--- a/spec/system/admin/account_moderation_notes_spec.rb
+++ b/spec/system/admin/account_moderation_notes_spec.rb
@@ -35,7 +35,7 @@ RSpec.describe 'Admin::AccountModerationNotes' do
     end
 
     def delete_note
-      within('.report-notes__item__actions') do
+      within('.report-notes__item:first-child .report-notes__item__actions') do
         click_on I18n.t('admin.reports.notes.delete')
       end
     end
diff --git a/spec/system/admin/instance/moderation_notes_spec.rb b/spec/system/admin/instance/moderation_notes_spec.rb
new file mode 100644
index 000000000..f8bf575b8
--- /dev/null
+++ b/spec/system/admin/instance/moderation_notes_spec.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin::Instances::ModerationNotesController' do
+  let(:current_user) { Fabricate(:admin_user) }
+  let(:instance_domain) { 'mastodon.example' }
+
+  before { sign_in current_user }
+
+  describe 'Managing instance moderation notes' do
+    it 'saves and then deletes a record' do
+      visit admin_instance_path(instance_domain)
+
+      fill_in 'instance_moderation_note_content', with: ''
+      expect { submit_form }
+        .to not_change(InstanceModerationNote, :count)
+      expect(page)
+        .to have_content(/error below/)
+
+      fill_in 'instance_moderation_note_content', with: 'Test message ' * InstanceModerationNote::CONTENT_SIZE_LIMIT
+      expect { submit_form }
+        .to not_change(InstanceModerationNote, :count)
+      expect(page)
+        .to have_content(/error below/)
+
+      fill_in 'instance_moderation_note_content', with: 'Test message'
+      expect { submit_form }
+        .to change(InstanceModerationNote, :count).by(1)
+      expect(page)
+        .to have_current_path(admin_instance_path(instance_domain))
+      expect(page)
+        .to have_content(I18n.t('admin.instances.moderation_notes.created_msg'))
+
+      expect { delete_note }
+        .to change(InstanceModerationNote, :count).by(-1)
+      expect(page)
+        .to have_content(I18n.t('admin.instances.moderation_notes.destroyed_msg'))
+    end
+
+    def submit_form
+      click_on I18n.t('admin.instances.moderation_notes.create')
+    end
+
+    def delete_note
+      within('.report-notes__item:first-child .report-notes__item__actions') do
+        click_on I18n.t('admin.reports.notes.delete')
+      end
+    end
+  end
+end