diff --git a/Gemfile b/Gemfile
index 473d9b60fd..4c23778ffc 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,7 @@ gem "activesupport", github: "rails/rails", branch: branch
 gem "activemodel", github: "rails/rails", branch: branch
 gem "activejob", github: "rails/rails", branch: branch
 gem "activerecord", github: "rails/rails", branch: branch
+gem "rack"
 gem "sqlite3", branch == "7-0-stable" ? "~> 1.4" : nil
 
 gem "rubocop"
@@ -18,6 +19,7 @@ gem "rubocop-performance"
 gem "rubocop-rails"
 gem "rubocop-rails-omakase"
 
+gem "minitest", "< 6"
 gem "minitest-bisect"
 
 gemspec
diff --git a/lib/active_resource/base.rb b/lib/active_resource/base.rb
index 10312bb6f5..c0dce6b65e 100644
--- a/lib/active_resource/base.rb
+++ b/lib/active_resource/base.rb
@@ -1151,7 +1151,34 @@ def all(*args)
 
       # This is an alias for all. You can pass in all the same
       # arguments to this method as you can to <tt>all</tt> and <tt>find(:all)</tt>
+      #
+      # #where accepts conditions in one of several formats. In the examples below, the resulting
+      # URL is given as an illustration.
+      #
+      # === \String
+      #
+      # A string is passed as URL query parameters.
+      #
+      #    Person.where("name=Matz")
+      #    # https://api.people.com/people.json?name=Matz
+      #
+      # === \Hash
+      #
+      # #where will also accept a hash condition, in which the keys are fields and the values
+      # are values to be searched for.
+      #
+      # Fields can be symbols or strings. Values can be single values, arrays, or ranges.
+      #
+      #   Person.where(name: "Matz")
+      #   # https://api.people.com/people.json?name=Matz
+      #
+      #   Person.where(person: { name: "Matz" })
+      #   # https://api.people.com/people.json?person[name]=Matz
+      #
+      #   Article.where(tags: ["Ruby", "Rails"])
+      #   # https://api.people.com/people.json?tags[]=Ruby&tags[]=Rails
       def where(clauses = {})
+        clauses = query_format.decode(clauses) if clauses.is_a?(String)
         clauses = sanitize_forbidden_attributes(clauses)
         raise ArgumentError, "expected a clauses Hash, got #{clauses.inspect}" unless clauses.is_a? Hash
         all(params: clauses)
diff --git a/lib/active_resource/formats/url_encoded_format.rb b/lib/active_resource/formats/url_encoded_format.rb
index dc69209fcb..6e3e19f111 100644
--- a/lib/active_resource/formats/url_encoded_format.rb
+++ b/lib/active_resource/formats/url_encoded_format.rb
@@ -1,16 +1,27 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/array/wrap"
-
 module ActiveResource
   module Formats
     module UrlEncodedFormat
       extend self
 
+      attr_accessor :query_parser # :nodoc:
+
       # URL encode the parameters Hash
       def encode(params, options = nil)
         params.to_query
       end
+
+      # URL decode the query string
+      def decode(query, remove_root = true)
+        query = query.delete_prefix("?")
+
+        if query_parser == :rack
+          Rack::Utils.parse_nested_query(query)
+        else
+          URI.decode_www_form(query).to_h
+        end
+      end
     end
   end
 end
diff --git a/lib/active_resource/railtie.rb b/lib/active_resource/railtie.rb
index 800f1208e2..e5f6b90197 100644
--- a/lib/active_resource/railtie.rb
+++ b/lib/active_resource/railtie.rb
@@ -39,5 +39,9 @@ class Railtie < Rails::Railtie
         teardown { ActiveResource::HttpMock.reset! }
       end
     end
+
+    config.after_initialize do
+      Formats::UrlEncodedFormat.query_parser ||= :rack if defined?(Rack::Utils)
+    end
   end
 end
diff --git a/lib/active_resource/where_clause.rb b/lib/active_resource/where_clause.rb
index c1072122d2..196cc22216 100644
--- a/lib/active_resource/where_clause.rb
+++ b/lib/active_resource/where_clause.rb
@@ -13,6 +13,7 @@ def initialize(resource_class, options = {})
     end
 
     def where(clauses = {})
+      clauses = @resource_class.query_format.decode(clauses) if clauses.is_a?(::String)
       all(params: clauses)
     end
 
diff --git a/test/cases/finder_test.rb b/test/cases/finder_test.rb
index 10326a1c65..4bd1d1c018 100644
--- a/test/cases/finder_test.rb
+++ b/test/cases/finder_test.rb
@@ -178,6 +178,33 @@ def test_where_clause_with_permitted_params
     assert_kind_of StreetAddress, addresses.first
   end
 
+  def test_where_clause_string
+    query = URI.encode_www_form([ [ "id", "1" ] ])
+    ActiveResource::HttpMock.respond_to { |m| m.get "/people.json?" + query, {}, @people_david }
+    people = Person.where(query)
+    assert_equal 1, people.size
+    assert_kind_of Person, people.first
+    assert_equal "David", people.first.name
+  end
+
+  def test_where_clause_string_chained
+    ActiveResource::HttpMock.respond_to { |m| m.get "/people.json?a=1&b=2&c=3&id=2", {}, @people_david }
+    people = Person.where("id=2").where(a: 1).where("b=2").where(c: 3)
+    assert_equal [ "David" ], people.map(&:name)
+  end
+
+  def test_where_clause_string_with_multiple_params
+    previous_query_parser = ActiveResource::Formats::UrlEncodedFormat.query_parser
+    ActiveResource::Formats::UrlEncodedFormat.query_parser = :rack
+
+    query = URI.encode_www_form([ [ "id[]", "1" ], [ "id[]", "2" ] ])
+    ActiveResource::HttpMock.respond_to { |m| m.get "/people.json?" + query, {}, @people }
+    people = Person.where(query)
+    assert_equal [ "Matz", "David" ], people.map(&:name)
+  ensure
+    ActiveResource::Formats::UrlEncodedFormat.query_parser = previous_query_parser
+  end
+
   def test_where_with_clause_in
     ActiveResource::HttpMock.respond_to { |m| m.get "/people.json?id%5B%5D=2", {}, @people_david }
     people = Person.where(id: [ 2 ])
diff --git a/test/cases/formats/url_encoded_format_test.rb b/test/cases/formats/url_encoded_format_test.rb
index a3342eecc7..bdca06c58b 100644
--- a/test/cases/formats/url_encoded_format_test.rb
+++ b/test/cases/formats/url_encoded_format_test.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "abstract_unit"
+require "rack/utils"
 
 class UrlEncodedFormatTest < ActiveSupport::TestCase
   test "#encode transforms a Hash into an application/x-www-form-urlencoded query string" do
@@ -10,4 +11,36 @@ class UrlEncodedFormatTest < ActiveSupport::TestCase
 
     assert_equal "a=1&b=2&c%5B%5D=3&c%5B%5D=4", encoded
   end
+
+  test "#encode transforms a nested Hash into an application/x-www-form-urlencoded query string" do
+    params = { "person" => { "name" => "Matz" } }
+
+    encoded = ActiveResource::Formats::UrlEncodedFormat.encode(params)
+
+    assert_equal "person%5Bname%5D=Matz", encoded
+  end
+
+  test "#decode transforms an application/x-www-form-urlencoded query string into a Hash" do
+    decoded = ActiveResource::Formats::UrlEncodedFormat.decode("a=1")
+
+    assert_equal({ "a" => "1" }, decoded)
+  end
+
+  test "#decode ignores a ?-prefix" do
+    decoded = ActiveResource::Formats::UrlEncodedFormat.decode("?a=1")
+
+    assert_equal({ "a" => "1" }, decoded)
+  end
+
+  test "#decode transforms an application/x-www-form-urlencoded query string with multiple params into a Hash" do
+    previous_query_parser = ActiveResource::Formats::UrlEncodedFormat.query_parser
+    ActiveResource::Formats::UrlEncodedFormat.query_parser = :rack
+    query = URI.encode_www_form([ [ "a[]", "1" ], [ "a[]", "2" ] ])
+
+    decoded = ActiveResource::Formats::UrlEncodedFormat.decode(query)
+
+    assert_equal({ "a" => [ "1", "2" ] }, decoded)
+  ensure
+    ActiveResource::Formats::UrlEncodedFormat.query_parser = previous_query_parser
+  end
 end