diff --git a/.changesets/add-helper-to-create-custom-markers-from-the-ruby-gem.md b/.changesets/add-helper-to-create-custom-markers-from-the-ruby-gem.md
new file mode 100644
index 00000000..7a97cf84
--- /dev/null
+++ b/.changesets/add-helper-to-create-custom-markers-from-the-ruby-gem.md
@@ -0,0 +1,31 @@
+---
+bump: minor
+type: add
+---
+
+Add a helper to create custom markers from the Ruby gem.
+
+Create a custom marker (a little icon shown in the graph timeline on AppSignal.com) to mark events on the timeline.
+
+Create a marker with all the available options:
+
+```ruby
+Appsignal::CustomMarker.report(
+  # The icon shown on the timeline
+  :icon => "🎉",
+  # The message shown on hover
+  :message => "Migration completed",
+  # Any time object or a string with a ISO8601 valid time is accepted
+  :created_at => Time.now
+)
+```
+
+Create a marker with just a message:
+
+```ruby
+Appsignal::CustomMarker.report(
+  :message => "Migration completed",
+)
+```
+
+_The default icon is the 🚀 icon. The default time is the time the request is received by our servers._
diff --git a/lib/appsignal.rb b/lib/appsignal.rb
index 1859ba99..b6f012d6 100644
--- a/lib/appsignal.rb
+++ b/lib/appsignal.rb
@@ -558,6 +558,7 @@ def collect_environment_metadata
 require "appsignal/hooks"
 require "appsignal/probes"
 require "appsignal/marker"
+require "appsignal/custom_marker"
 require "appsignal/garbage_collection"
 require "appsignal/rack"
 require "appsignal/rack/body_wrapper"
diff --git a/lib/appsignal/custom_marker.rb b/lib/appsignal/custom_marker.rb
new file mode 100644
index 00000000..e5c60306
--- /dev/null
+++ b/lib/appsignal/custom_marker.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+module Appsignal
+  # Custom markers are used on AppSignal.com to indicate events in an
+  # application, to give additional context on graph timelines.
+  #
+  # This helper class will send a request to the AppSignal public endpoint to
+  # create a Custom marker for the application on AppSignal.com.
+  #
+  # @see https://docs.appsignal.com/api/public-endpoint/custom-markers.html
+  #   Public Endpoint API markers endpoint documentation
+  # @see https://docs.appsignal.com/appsignal/terminology.html#markers
+  #   Terminology: Markers
+  class CustomMarker
+    # @param icon [String] icon to use for the marker, like an emoji.
+    # @param message [String] name of the user that is creating the
+    #   marker.
+    # @param created_at [Time/String] A Ruby time object or a valid ISO8601
+    #   timestamp.
+    # @return [Boolean]
+    def self.report(
+      icon: nil,
+      message: nil,
+      created_at: nil
+    )
+      new(
+        {
+          :icon => icon,
+          :message => message,
+          :created_at => created_at.respond_to?(:iso8601) ? created_at.iso8601 : created_at
+        }.compact
+      ).transmit
+    end
+
+    # @api private
+    def initialize(marker_data)
+      @marker_data = marker_data
+    end
+
+    # @api private
+    def transmit
+      unless Appsignal.config
+        Appsignal.internal_logger.warn(
+          "Did not transmit custom marker: no AppSignal config loaded"
+        )
+        return false
+      end
+
+      transmitter = Transmitter.new(
+        "#{Appsignal.config[:logging_endpoint]}/markers",
+        Appsignal.config
+      )
+      response = transmitter.transmit(@marker_data)
+
+      if (200...300).include?(response.code.to_i)
+        Appsignal.internal_logger.info("Transmitted custom marker")
+        true
+      else
+        Appsignal.internal_logger.error(
+          "Failed to transmit custom marker: #{response.code} status code"
+        )
+        false
+      end
+    rescue => e
+      Appsignal.internal_logger.error(
+        "Failed to transmit custom marker: #{e.class}: #{e.message}\n" \
+          "#{e.backtrace}"
+      )
+      false
+    end
+  end
+end
diff --git a/spec/lib/appsignal/custom_marker_spec.rb b/spec/lib/appsignal/custom_marker_spec.rb
new file mode 100644
index 00000000..4e727983
--- /dev/null
+++ b/spec/lib/appsignal/custom_marker_spec.rb
@@ -0,0 +1,155 @@
+describe Appsignal::CustomMarker do
+  let(:config) { build_config }
+
+  describe "#transmit" do
+    # def stub_marker_request
+    #   stub_api_request config, "markers", marker.marker_data
+    # end
+
+    def create_marker(
+      icon: nil,
+      message: nil,
+      created_at: nil
+    )
+      described_class.report(
+        :icon => icon,
+        :message => message,
+        :created_at => created_at
+      )
+    end
+
+    context "without Appsignal.config" do
+      it "logs a warning" do
+        logs =
+          capture_logs do
+            expect(create_marker(
+              :icon => "🎉",
+              :message => "Migration completed",
+              :created_at => Time.now
+            )).to be(false)
+          end
+        expect(logs)
+          .to contains_log(:warn, "Did not transmit custom marker: no AppSignal config loaded")
+      end
+    end
+
+    context "with Appsignal.config" do
+      before { configure }
+
+      context "when request is valid" do
+        it "sends request with all parameters and logs success" do
+          time = "2025-02-21T11:03:48+01:00"
+          stub_public_endpoint_markers_request(
+            :marker_data => {
+              "icon" => "🎉",
+              "message" => "Migration completed",
+              "created_at" => time
+            }
+          ).to_return(:status => 200)
+
+          logs =
+            capture_logs do
+              expect(create_marker(
+                :icon => "🎉",
+                :message => "Migration completed",
+                :created_at => time
+              )).to be(true)
+            end
+
+          expect(logs).to contains_log(:info, "Transmitted custom marker")
+          expect(logs).to_not contains_log(:error, "Failed to transmit custom marker")
+        end
+
+        it "sends request with time object as parameter and logs success" do
+          time = Time.now.utc
+          stub_public_endpoint_markers_request(
+            :marker_data => {
+              "icon" => "🎉",
+              "message" => "Migration completed",
+              "created_at" => time.iso8601
+            }
+          ).to_return(:status => 200)
+
+          logs =
+            capture_logs do
+              expect(create_marker(
+                :icon => "🎉",
+                :message => "Migration completed",
+                :created_at => time
+              )).to be(true)
+            end
+
+          expect(logs).to contains_log(:info, "Transmitted custom marker")
+          expect(logs).to_not contains_log(:error, "Failed to transmit custom marker")
+        end
+
+        it "sends request with some parameters and logs success" do
+          stub_public_endpoint_markers_request(
+            :marker_data => {
+              "message" => "Migration completed"
+            }
+          ).to_return(:status => 200)
+
+          logs =
+            capture_logs do
+              expect(create_marker(:message => "Migration completed")).to be(true)
+            end
+
+          expect(logs).to contains_log(:info, "Transmitted custom marker")
+          expect(logs).to_not contains_log(:error, "Failed to transmit custom marker")
+        end
+      end
+
+      context "when request failed" do
+        it "logs error" do
+          time = Time.now.utc
+          stub_public_endpoint_markers_request(
+            :marker_data => {
+              "icon" => "🎉",
+              "message" => "Migration completed",
+              "created_at" => time.iso8601
+            }
+          ).to_return(:status => 500)
+
+          logs =
+            capture_logs do
+              expect(create_marker(
+                :icon => "🎉",
+                :message => "Migration completed",
+                :created_at => time
+              )).to be(false)
+            end
+
+          expect(logs).to_not contains_log(:info, "Transmitted custom marker")
+          expect(logs).to contains_log(:error, "Failed to transmit custom marker: 500 status code")
+        end
+      end
+
+      context "when request raised an error" do
+        it "logs error" do
+          time = Time.now.utc
+          stub_public_endpoint_markers_request(
+            :marker_data => {
+              "icon" => "🎉",
+              "message" => "Migration completed",
+              "created_at" => time.iso8601
+            }
+          ).to_raise(RuntimeError.new("uh oh"))
+
+          logs =
+            capture_logs do
+              expect(create_marker(
+                :icon => "🎉",
+                :message => "Migration completed",
+                :created_at => time
+              )).to be(false)
+            end
+
+          expect(logs).to_not contains_log(:info, "Transmitted custom marker")
+          expect(logs)
+            .to contains_log(:error, "Failed to transmit custom marker: RuntimeError: uh oh")
+        end
+      end
+    end
+  end
+end
diff --git a/spec/support/helpers/api_request_helper.rb b/spec/support/helpers/api_request_helper.rb
index 192a2495..9250a30e 100644
--- a/spec/support/helpers/api_request_helper.rb
+++ b/spec/support/helpers/api_request_helper.rb
@@ -30,6 +30,27 @@ def stub_api_request(config, path, body = nil)
     stub_request(:post, "#{endpoint}/1/#{path}").with(options)
   end
 
+  def stub_public_endpoint_markers_request(marker_data:)
+    config = Appsignal.config
+    options = {
+      :query => {
+        :api_key => config[:push_api_key],
+        :name => config[:name],
+        :environment => config.respond_to?(:env) ? config.env : config[:environment],
+        :hostname => config[:hostname],
+        :gem_version => Appsignal::VERSION
+      },
+      :headers => { "Content-Type" => "application/json; charset=UTF-8" }
+    }
+    stub_request(
+      :post,
+      "#{config[:logging_endpoint]}/markers"
+    ).with(options) do |request|
+      payload = JSON.parse(request.body)
+      expect(payload).to match(marker_data)
+    end
+  end
+
   def stub_cron_check_in_request(events:, response: { :status => 200 })
     stub_check_in_requests(
       :requests => [events],