diff --git a/config/feature_flags/development/ci_multi_doc_yaml.yml b/config/feature_flags/development/ci_multi_doc_yaml.yml
new file mode 100644
index 0000000000000000000000000000000000000000..4e6289abefa492366579afcba23e65984584eeb9
--- /dev/null
+++ b/config/feature_flags/development/ci_multi_doc_yaml.yml
@@ -0,0 +1,8 @@
+---
+name: ci_multi_doc_yaml
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/109137
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/388836
+milestone: '15.9'
+type: development
+group: group::pipeline authoring
+default_enabled: false
diff --git a/lib/gitlab/ci/config.rb b/lib/gitlab/ci/config.rb
index 142f0b8dfd8c3e0960bcf3b4fe0f3e9a3f628598..585e671ce426be3b81f27e631d153889eb5a544d 100644
--- a/lib/gitlab/ci/config.rb
+++ b/lib/gitlab/ci/config.rb
@@ -117,7 +117,8 @@ def metadata
       def expand_config(config)
         build_config(config)
 
-      rescue Gitlab::Config::Loader::Yaml::DataTooLargeError => e
+      rescue Gitlab::Config::Loader::Yaml::DataTooLargeError,
+        Gitlab::Config::Loader::MultiDocYaml::DataTooLargeError => e
         track_and_raise_for_dev_exception(e)
         raise Config::ConfigError, e.message
 
diff --git a/lib/gitlab/ci/config/yaml.rb b/lib/gitlab/ci/config/yaml.rb
index de833619c8df2469f7223cedd790caf4b5332c87..94ef0afe7f9fa45e3f5e3c99ca4b2d2ab9d015a2 100644
--- a/lib/gitlab/ci/config/yaml.rb
+++ b/lib/gitlab/ci/config/yaml.rb
@@ -5,12 +5,21 @@ module Ci
     class Config
       module Yaml
         AVAILABLE_TAGS = [Config::Yaml::Tags::Reference].freeze
+        MAX_DOCUMENTS = 2
 
         class << self
           def load!(content)
             ensure_custom_tags
 
-            Gitlab::Config::Loader::Yaml.new(content, additional_permitted_classes: AVAILABLE_TAGS).load!
+            if ::Feature.enabled?(:ci_multi_doc_yaml)
+              Gitlab::Config::Loader::MultiDocYaml.new(
+                content,
+                max_documents: MAX_DOCUMENTS,
+                additional_permitted_classes: AVAILABLE_TAGS
+              ).load!.first
+            else
+              Gitlab::Config::Loader::Yaml.new(content, additional_permitted_classes: AVAILABLE_TAGS).load!
+            end
           end
 
           private
diff --git a/lib/gitlab/config/loader/multi_doc_yaml.rb b/lib/gitlab/config/loader/multi_doc_yaml.rb
new file mode 100644
index 0000000000000000000000000000000000000000..346adc79896c5bdd70000a35ee7d8dcd13db88bd
--- /dev/null
+++ b/lib/gitlab/config/loader/multi_doc_yaml.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Config
+    module Loader
+      class MultiDocYaml
+        TooManyDocumentsError = Class.new(Loader::FormatError)
+        DataTooLargeError = Class.new(Loader::FormatError)
+        NotHashError = Class.new(Loader::FormatError)
+
+        MULTI_DOC_DIVIDER = /^---$/.freeze
+
+        def initialize(config, max_documents:, additional_permitted_classes: [])
+          @max_documents = max_documents
+          @safe_config = load_config(config, additional_permitted_classes)
+        end
+
+        def load!
+          raise TooManyDocumentsError, 'The parsed YAML has too many documents' if too_many_documents?
+          raise DataTooLargeError, 'The parsed YAML is too big' if too_big?
+          raise NotHashError, 'Invalid configuration format' unless all_hashes?
+
+          safe_config.map(&:deep_symbolize_keys)
+        end
+
+        private
+
+        attr_reader :safe_config, :max_documents
+
+        def load_config(config, additional_permitted_classes)
+          config.split(MULTI_DOC_DIVIDER).filter_map do |document|
+            YAML.safe_load(document,
+              permitted_classes: [Symbol, *additional_permitted_classes],
+              permitted_symbols: [],
+              aliases: true
+            )
+          end
+        rescue Psych::Exception => e
+          raise Loader::FormatError, e.message
+        end
+
+        def all_hashes?
+          safe_config.all?(Hash)
+        end
+
+        def too_many_documents?
+          safe_config.count > max_documents
+        end
+
+        def too_big?
+          !deep_sizes.all?(&:valid?)
+        end
+
+        def deep_sizes
+          safe_config.map do |config|
+            Gitlab::Utils::DeepSize.new(config,
+              max_size: Gitlab::CurrentSettings.current_application_settings.max_yaml_size_bytes,
+              max_depth: Gitlab::CurrentSettings.current_application_settings.max_yaml_depth)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/ci/config/yaml_spec.rb b/spec/lib/gitlab/ci/config/yaml_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..4b34553f55e58660e165fd65d6775038324795d2
--- /dev/null
+++ b/spec/lib/gitlab/ci/config/yaml_spec.rb
@@ -0,0 +1,105 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Ci::Config::Yaml, feature_category: :pipeline_authoring do
+  describe '.load!' do
+    it 'loads a single-doc YAML file' do
+      yaml = <<~YAML
+      image: 'image:1.0'
+      texts:
+        nested_key: 'value1'
+        more_text:
+          more_nested_key: 'value2'
+      YAML
+
+      config = described_class.load!(yaml)
+
+      expect(config).to eq({
+        image: 'image:1.0',
+        texts: {
+          nested_key: 'value1',
+          more_text: {
+            more_nested_key: 'value2'
+          }
+        }
+      })
+    end
+
+    it 'loads the first document from a multi-doc YAML file' do
+      yaml = <<~YAML
+      spec:
+        inputs:
+          test_input:
+      ---
+      image: 'image:1.0'
+      texts:
+        nested_key: 'value1'
+        more_text:
+          more_nested_key: 'value2'
+      YAML
+
+      config = described_class.load!(yaml)
+
+      expect(config).to eq({
+        spec: {
+          inputs: {
+            test_input: nil
+          }
+        }
+      })
+    end
+
+    context 'when ci_multi_doc_yaml is disabled' do
+      before do
+        stub_feature_flags(ci_multi_doc_yaml: false)
+      end
+
+      it 'loads a single-doc YAML file' do
+        yaml = <<~YAML
+        image: 'image:1.0'
+        texts:
+          nested_key: 'value1'
+          more_text:
+            more_nested_key: 'value2'
+        YAML
+
+        config = described_class.load!(yaml)
+
+        expect(config).to eq({
+          image: 'image:1.0',
+          texts: {
+            nested_key: 'value1',
+            more_text: {
+              more_nested_key: 'value2'
+            }
+          }
+        })
+      end
+
+      it 'loads the first document from a multi-doc YAML file' do
+        yaml = <<~YAML
+        spec:
+          inputs:
+            test_input:
+        ---
+        image: 'image:1.0'
+        texts:
+          nested_key: 'value1'
+          more_text:
+            more_nested_key: 'value2'
+        YAML
+
+        config = described_class.load!(yaml)
+
+        expect(config).to eq({
+          spec: {
+            inputs: {
+              test_input: nil
+            }
+          }
+        })
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/config/loader/multi_doc_yaml_spec.rb b/spec/lib/gitlab/config/loader/multi_doc_yaml_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..bae98f9bc3557590f2d77ad8e8fa280d897da2c1
--- /dev/null
+++ b/spec/lib/gitlab/config/loader/multi_doc_yaml_spec.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Config::Loader::MultiDocYaml, feature_category: :pipeline_authoring do
+  let(:loader) { described_class.new(yml, max_documents: 2) }
+
+  describe '#load!' do
+    let(:yml) do
+      <<~YAML
+      spec:
+        inputs:
+          test_input:
+      ---
+      test_job:
+        script: echo "$[[ inputs.test_input ]]"
+      YAML
+    end
+
+    it 'returns the loaded YAML with all keys as symbols' do
+      expect(loader.load!).to eq([
+        { spec: { inputs: { test_input: nil } } },
+        { test_job: { script: 'echo "$[[ inputs.test_input ]]"' } }
+      ])
+    end
+
+    context 'when the YAML file is empty' do
+      let(:yml) { '' }
+
+      it 'returns an empty array' do
+        expect(loader.load!).to be_empty
+      end
+    end
+
+    context 'when the parsed YAML is too big' do
+      let(:yml) do
+        <<~YAML
+        a: &a ["lol","lol","lol","lol","lol","lol","lol","lol","lol"]
+        b: &b [*a,*a,*a,*a,*a,*a,*a,*a,*a]
+        c: &c [*b,*b,*b,*b,*b,*b,*b,*b,*b]
+        d: &d [*c,*c,*c,*c,*c,*c,*c,*c,*c]
+        e: &e [*d,*d,*d,*d,*d,*d,*d,*d,*d]
+        f: &f [*e,*e,*e,*e,*e,*e,*e,*e,*e]
+        g: &g [*f,*f,*f,*f,*f,*f,*f,*f,*f]
+        h: &h [*g,*g,*g,*g,*g,*g,*g,*g,*g]
+        i: &i [*h,*h,*h,*h,*h,*h,*h,*h,*h]
+        ---
+        a: &a ["lol","lol","lol","lol","lol","lol","lol","lol","lol"]
+        b: &b [*a,*a,*a,*a,*a,*a,*a,*a,*a]
+        c: &c [*b,*b,*b,*b,*b,*b,*b,*b,*b]
+        d: &d [*c,*c,*c,*c,*c,*c,*c,*c,*c]
+        e: &e [*d,*d,*d,*d,*d,*d,*d,*d,*d]
+        f: &f [*e,*e,*e,*e,*e,*e,*e,*e,*e]
+        g: &g [*f,*f,*f,*f,*f,*f,*f,*f,*f]
+        h: &h [*g,*g,*g,*g,*g,*g,*g,*g,*g]
+        i: &i [*h,*h,*h,*h,*h,*h,*h,*h,*h]
+        YAML
+      end
+
+      it 'raises a DataTooLargeError' do
+        expect { loader.load! }.to raise_error(described_class::DataTooLargeError, 'The parsed YAML is too big')
+      end
+    end
+
+    context 'when a document is not a hash' do
+      let(:yml) do
+        <<~YAML
+        not_a_hash
+        ---
+        test_job:
+          script: echo "$[[ inputs.test_input ]]"
+        YAML
+      end
+
+      it 'raises a NotHashError' do
+        expect { loader.load! }.to raise_error(described_class::NotHashError, 'Invalid configuration format')
+      end
+    end
+
+    context 'when there are too many documents' do
+      let(:yml) do
+        <<~YAML
+        a: b
+        ---
+        c: d
+        ---
+        e: f
+        YAML
+      end
+
+      it 'raises a TooManyDocumentsError' do
+        expect { loader.load! }.to raise_error(
+          described_class::TooManyDocumentsError,
+          'The parsed YAML has too many documents'
+        )
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/config/loader/yaml_spec.rb b/spec/lib/gitlab/config/loader/yaml_spec.rb
index c7f84cd583c9d1163b7935a0675667993f2453ef..346424d1681429568a2a85f48100ebec2173b90d 100644
--- a/spec/lib/gitlab/config/loader/yaml_spec.rb
+++ b/spec/lib/gitlab/config/loader/yaml_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::Config::Loader::Yaml do
+RSpec.describe Gitlab::Config::Loader::Yaml, feature_category: :pipeline_authoring do
   let(:loader) { described_class.new(yml) }
 
   let(:yml) do