diff --git a/app/services/create_collection_service.rb b/app/services/create_collection_service.rb
new file mode 100644
index 00000000000..5cf7249fee4
--- /dev/null
+++ b/app/services/create_collection_service.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+class CreateCollectionService
+  def call(params, account)
+    tag = params.delete(:tag)
+    account_ids = params.delete(:account_ids)
+    @collection = Collection.new(params.merge({ account:, local: true, tag: find_or_create_tag(tag) }))
+    build_items(account_ids)
+
+    @collection.save!
+    @collection
+  end
+
+  private
+
+  def find_or_create_tag(name)
+    return nil if name.blank?
+
+    Tag.find_or_create_by_names(name).first
+  end
+
+  def build_items(account_ids)
+    return if account_ids.blank?
+
+    account_ids.each do |account_id|
+      account = Account.find(account_id)
+      # TODO: validate preferences
+      @collection.collection_items.build(account:)
+    end
+  end
+end
diff --git a/spec/services/create_collection_service_spec.rb b/spec/services/create_collection_service_spec.rb
new file mode 100644
index 00000000000..43842c8cc65
--- /dev/null
+++ b/spec/services/create_collection_service_spec.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe CreateCollectionService do
+  subject { described_class.new }
+
+  let(:author) { Fabricate.create(:account) }
+
+  describe '#call' do
+    let(:base_params) do
+      {
+        name: 'People to follow',
+        description: 'All my favourites',
+        sensitive: false,
+        discoverable: true,
+      }
+    end
+
+    context 'when given valid parameters' do
+      it 'creates a new local collection' do
+        collection = nil
+
+        expect do
+          collection = subject.call(base_params, author)
+        end.to change(Collection, :count).by(1)
+
+        expect(collection).to be_a(Collection)
+        expect(collection).to be_local
+      end
+
+      context 'when given account ids' do
+        let(:account_ids) do
+          Fabricate.times(2, :account).map { |a| a.id.to_s }
+        end
+        let(:params) do
+          base_params.merge(account_ids:)
+        end
+
+        it 'also creates collection items' do
+          expect do
+            subject.call(params, author)
+          end.to change(CollectionItem, :count).by(2)
+        end
+      end
+
+      context 'when given a tag' do
+        let(:params) { base_params.merge(tag: '#people') }
+
+        context 'when the tag exists' do
+          let!(:tag) { Fabricate.create(:tag, name: 'people') }
+
+          it 'correctly assigns the existing tag' do
+            collection = subject.call(params, author)
+
+            expect(collection.tag).to eq tag
+          end
+        end
+
+        context 'when the tag does not exist' do
+          it 'creates a new tag' do
+            collection = nil
+
+            expect do
+              collection = subject.call(params, author)
+            end.to change(Tag, :count).by(1)
+
+            expect(collection.tag.name).to eq 'people'
+          end
+        end
+      end
+    end
+
+    context 'when given invalid parameters' do
+      it 'raises an exception' do
+        expect do
+          subject.call({}, author)
+        end.to raise_error(ActiveRecord::RecordInvalid)
+      end
+    end
+  end
+end