diff --git a/lib/httpx/options.rb b/lib/httpx/options.rb
index ece26f64..02b1c5a6 100644
--- a/lib/httpx/options.rb
+++ b/lib/httpx/options.rb
@@ -88,6 +88,10 @@ module HTTPX
       end
     end
 
+    def_option(:origin, <<-OUT)
+      URI(value)
+    OUT
+
     def_option(:headers, <<-OUT)
       if self.headers
         self.headers.merge(value)
diff --git a/lib/httpx/request.rb b/lib/httpx/request.rb
index dc502639..fd19c56e 100644
--- a/lib/httpx/request.rb
+++ b/lib/httpx/request.rb
@@ -41,8 +41,13 @@ module HTTPX
 
     def initialize(verb, uri, options = {})
       @verb    = verb.to_s.downcase.to_sym
-      @uri     = Utils.uri(uri)
       @options = Options.new(options)
+      @uri     = Utils.uri(uri)
+      if @uri.relative?
+        raise(Error, "invalid URI: #{@uri}") unless @options.origin
+
+        @uri = @options.origin.merge(@uri)
+      end
 
       raise(Error, "unknown method: #{verb}") unless METHODS.include?(@verb)
 
diff --git a/sig/options.rbs b/sig/options.rbs
index 7146db43..f61917ca 100644
--- a/sig/options.rbs
+++ b/sig/options.rbs
@@ -11,6 +11,10 @@ module HTTPX
     def self.new: (options) -> instance
                 | () -> instance
 
+    # headers
+    attr_reader uri: URI?
+    def uri=: (uri) -> void
+
     # headers
     attr_reader headers: Headers?
     def headers=: (headers) -> void
diff --git a/test/error_response_test.rb b/test/error_response_test.rb
index a4607c8d..dd5de26d 100644
--- a/test/error_response_test.rb
+++ b/test/error_response_test.rb
@@ -33,6 +33,6 @@ class ErrorResponseTest < Minitest::Test
   private
 
   def request_mock
-    Request.new(:get, "/")
+    Request.new(:get, "http://example.com/")
   end
 end
diff --git a/test/request_test.rb b/test/request_test.rb
index 39a9430f..fde0bebc 100644
--- a/test/request_test.rb
+++ b/test/request_test.rb
@@ -6,14 +6,14 @@ class RequestTest < Minitest::Test
   include HTTPX
 
   def test_request_unsupported_body
-    ex = assert_raises(HTTPX::Error) { Request.new(:post, "/", body: Object.new) }
+    ex = assert_raises(HTTPX::Error) { Request.new(:post, "http://example.com/", body: Object.new) }
     assert ex.message =~ /cannot determine size of body/
   end
 
   def test_request_verb
-    r1 = Request.new(:get, "/")
+    r1 = Request.new(:get, "http://example.com/")
     assert r1.verb == :get, "unexpected verb (#{r1.verb})"
-    r2 = Request.new("GET", "/")
+    r2 = Request.new("GET", "http://example.com/")
     assert r2.verb == :get, "unexpected verb (#{r1.verb})"
   end
 
@@ -57,21 +57,21 @@ class RequestTest < Minitest::Test
   end
 
   def test_request_body_raw
-    req = Request.new(:post, "/", body: "bang")
+    req = Request.new(:post, "http://example.com/", body: "bang")
     assert !req.body.empty?, "body should exist"
     assert req.headers["content-type"] == "application/octet-stream", "content type is wrong"
     assert req.headers["content-length"] == "4", "content length is wrong"
   end
 
   def test_request_body_form
-    req = Request.new(:post, "/", form: { "foo" => "bar" })
+    req = Request.new(:post, "http://example.com/", form: { "foo" => "bar" })
     assert !req.body.empty?, "body should exist"
     assert req.headers["content-type"] == "application/x-www-form-urlencoded", "content type is wrong"
     assert req.headers["content-length"] == "7", "content length is wrong"
   end
 
   def test_request_body_json
-    req = Request.new(:post, "/", json: { "foo" => "bar" })
+    req = Request.new(:post, "http://example.com/", json: { "foo" => "bar" })
     assert !req.body.empty?, "body should exist"
     assert req.headers["content-type"] == "application/json; charset=utf-8", "content type is wrong"
     assert req.headers["content-length"] == "13", "content length is wrong"
diff --git a/test/session_test.rb b/test/session_test.rb
index 7a80c5d6..7ead3a79 100644
--- a/test/session_test.rb
+++ b/test/session_test.rb
@@ -27,7 +27,7 @@ class SessionTest < Minitest::Test
     assert session.options.respond_to?(:foo), "options methods weren't added"
     assert session.options.foo == "options-foo", "option method is unexpected"
 
-    request = session.options.request_class.new(:get, "/", session.options)
+    request = session.options.request_class.new(:get, "http://example.com/", session.options)
     assert request.respond_to?(:foo), "request methods haven't been added"
     assert request.foo == "request-foo", "request method is unexpected"
     assert request.headers.respond_to?(:foo), "headers methods haven't been added"
diff --git a/test/support/requests/get.rb b/test/support/requests/get.rb
index e4d7083c..be77d4e1 100644
--- a/test/support/requests/get.rb
+++ b/test/support/requests/get.rb
@@ -3,6 +3,8 @@
 require "time"
 
 module Requests
+  using HTTPX::URIExtensions
+
   module Get
     def test_http_get
       uri = build_uri("/get")
@@ -11,6 +13,13 @@ module Requests
       verify_body_length(response)
     end
 
+    def test_http_get_option_origin
+      uri = URI(build_uri("/get"))
+      response = HTTPX.with(origin: uri.origin).get(uri.path)
+      verify_status(response, 200)
+      verify_body_length(response)
+    end
+
     def test_http_request
       uri = build_uri("/get")
       response = HTTPX.request(:get, uri)