diff --git a/spec/std/system/group_spec.cr b/spec/std/system/group_spec.cr
index 5c55611e4d28..ba511d03a05c 100644
--- a/spec/std/system/group_spec.cr
+++ b/spec/std/system/group_spec.cr
@@ -1,10 +1,14 @@
-{% skip_file if flag?(:win32) %}
-
 require "spec"
 require "system/group"
 
-GROUP_NAME         = {{ `id -gn`.stringify.chomp }}
-GROUP_ID           = {{ `id -g`.stringify.chomp }}
+{% if flag?(:win32) %}
+  GROUP_NAME = "BUILTIN\\Administrators"
+  GROUP_ID   = "S-1-5-32-544"
+{% else %}
+  GROUP_NAME = {{ `id -gn`.stringify.chomp }}
+  GROUP_ID   = {{ `id -g`.stringify.chomp }}
+{% end %}
+
 INVALID_GROUP_NAME = "this_group_does_not_exist"
 INVALID_GROUP_ID   = {% if flag?(:android) %}"8888"{% else %}"1234567"{% end %}
 
diff --git a/src/crystal/system/group.cr b/src/crystal/system/group.cr
index 8a542e2cc63c..6cb93739a900 100644
--- a/src/crystal/system/group.cr
+++ b/src/crystal/system/group.cr
@@ -12,6 +12,8 @@ end
   require "./wasi/group"
 {% elsif flag?(:unix) %}
   require "./unix/group"
+{% elsif flag?(:win32) %}
+  require "./win32/group"
 {% else %}
   {% raise "No Crystal::System::Group implementation available" %}
 {% end %}
diff --git a/src/crystal/system/win32/group.cr b/src/crystal/system/win32/group.cr
new file mode 100644
index 000000000000..3b40774ac2d8
--- /dev/null
+++ b/src/crystal/system/win32/group.cr
@@ -0,0 +1,82 @@
+require "crystal/system/windows"
+
+# This file contains source code derived from the following:
+#
+# * https://cs.opensource.google/go/go/+/refs/tags/go1.23.0:src/os/user/lookup_windows.go
+# * https://cs.opensource.google/go/go/+/refs/tags/go1.23.0:src/syscall/security_windows.go
+#
+# The following is their license:
+#
+# Copyright 2009 The Go Authors.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#    * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#    * Neither the name of Google LLC nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+module Crystal::System::Group
+  def initialize(@name : String, @id : String)
+  end
+
+  def system_name : String
+    @name
+  end
+
+  def system_id : String
+    @id
+  end
+
+  def self.from_name?(groupname : String) : ::System::Group?
+    if found = Crystal::System.name_to_sid(groupname)
+      from_sid(found.sid)
+    end
+  end
+
+  def self.from_id?(groupid : String) : ::System::Group?
+    if sid = Crystal::System.sid_from_s(groupid)
+      begin
+        from_sid(sid)
+      ensure
+        LibC.LocalFree(sid)
+      end
+    end
+  end
+
+  private def self.from_sid(sid : LibC::SID*) : ::System::Group?
+    canonical = Crystal::System.sid_to_name(sid) || return
+
+    # https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-samr/7b2aeb27-92fc-41f6-8437-deb65d950921#gt_0387e636-5654-4910-9519-1f8326cf5ec0
+    # SidTypeAlias should also be treated as a group type next to SidTypeGroup
+    # and SidTypeWellKnownGroup:
+    # "alias object -> resource group: A group object..."
+    #
+    # Tests show that "Administrators" can be considered of type SidTypeAlias.
+    case canonical.type
+    when .sid_type_group?, .sid_type_well_known_group?, .sid_type_alias?
+      domain_and_group = canonical.domain.empty? ? canonical.name : "#{canonical.domain}\\#{canonical.name}"
+      gid = Crystal::System.sid_to_s(sid)
+      ::System::Group.new(domain_and_group, gid)
+    end
+  end
+end
diff --git a/src/crystal/system/win32/user.cr b/src/crystal/system/win32/user.cr
index e5fcdbba10aa..4a06570c72b8 100644
--- a/src/crystal/system/win32/user.cr
+++ b/src/crystal/system/win32/user.cr
@@ -1,4 +1,4 @@
-require "c/sddl"
+require "crystal/system/windows"
 require "c/lm"
 require "c/userenv"
 require "c/security"
@@ -71,7 +71,7 @@ module Crystal::System::User
   end
 
   def self.from_username?(username : String) : ::System::User?
-    if found = name_to_sid(username)
+    if found = Crystal::System.name_to_sid(username)
       if found.type.sid_type_user?
         from_sid(found.sid)
       end
@@ -79,7 +79,7 @@ module Crystal::System::User
   end
 
   def self.from_id?(id : String) : ::System::User?
-    if sid = sid_from_s(id)
+    if sid = Crystal::System.sid_from_s(id)
       begin
         from_sid(sid)
       ensure
@@ -89,13 +89,13 @@ module Crystal::System::User
   end
 
   private def self.from_sid(sid : LibC::SID*) : ::System::User?
-    canonical = sid_to_name(sid) || return
+    canonical = Crystal::System.sid_to_name(sid) || return
     return unless canonical.type.sid_type_user?
 
     domain_and_user = "#{canonical.domain}\\#{canonical.name}"
     full_name = lookup_full_name(canonical.name, canonical.domain, domain_and_user) || return
     pgid = lookup_primary_group_id(canonical.name, canonical.domain) || return
-    uid = sid_to_s(sid)
+    uid = Crystal::System.sid_to_s(sid)
     home_dir = lookup_home_directory(uid, canonical.name) || return
 
     ::System::User.new(domain_and_user, uid, pgid, full_name, home_dir)
@@ -136,10 +136,10 @@ module Crystal::System::User
   # https://support.microsoft.com/en-us/help/297951/how-to-use-the-primarygroupid-attribute-to-find-the-primary-group-for
   # The method follows this formula: domainRID + "-" + primaryGroupRID
   private def self.lookup_primary_group_id(name : String, domain : String) : String?
-    domain_sid = name_to_sid(domain) || return
+    domain_sid = Crystal::System.name_to_sid(domain) || return
     return unless domain_sid.type.sid_type_domain?
 
-    domain_sid_str = sid_to_s(domain_sid.sid)
+    domain_sid_str = Crystal::System.sid_to_s(domain_sid.sid)
 
     # If the user has joined a domain use the RID of the default primary group
     # called "Domain Users":
@@ -210,43 +210,6 @@ module Crystal::System::User
     return "#{profile_dir}\\#{username}" if profile_dir
   end
 
-  private record SIDLookupResult, sid : LibC::SID*, domain : String, type : LibC::SID_NAME_USE
-
-  private def self.name_to_sid(name : String) : SIDLookupResult?
-    utf16_name = Crystal::System.to_wstr(name)
-
-    sid_size = LibC::DWORD.zero
-    domain_buf_size = LibC::DWORD.zero
-    LibC.LookupAccountNameW(nil, utf16_name, nil, pointerof(sid_size), nil, pointerof(domain_buf_size), out _)
-
-    unless WinError.value.error_none_mapped?
-      sid = Pointer(UInt8).malloc(sid_size).as(LibC::SID*)
-      domain_buf = Slice(LibC::WCHAR).new(domain_buf_size)
-      if LibC.LookupAccountNameW(nil, utf16_name, sid, pointerof(sid_size), domain_buf, pointerof(domain_buf_size), out sid_type) != 0
-        domain = String.from_utf16(domain_buf[..-2])
-        SIDLookupResult.new(sid, domain, sid_type)
-      end
-    end
-  end
-
-  private record NameLookupResult, name : String, domain : String, type : LibC::SID_NAME_USE
-
-  private def self.sid_to_name(sid : LibC::SID*) : NameLookupResult?
-    name_buf_size = LibC::DWORD.zero
-    domain_buf_size = LibC::DWORD.zero
-    LibC.LookupAccountSidW(nil, sid, nil, pointerof(name_buf_size), nil, pointerof(domain_buf_size), out _)
-
-    unless WinError.value.error_none_mapped?
-      name_buf = Slice(LibC::WCHAR).new(name_buf_size)
-      domain_buf = Slice(LibC::WCHAR).new(domain_buf_size)
-      if LibC.LookupAccountSidW(nil, sid, name_buf, pointerof(name_buf_size), domain_buf, pointerof(domain_buf_size), out sid_type) != 0
-        name = String.from_utf16(name_buf[..-2])
-        domain = String.from_utf16(domain_buf[..-2])
-        NameLookupResult.new(name, domain, sid_type)
-      end
-    end
-  end
-
   private def self.domain_joined? : Bool
     status = LibC.NetGetJoinInformation(nil, out domain, out type)
     if status != LibC::NERR_Success
@@ -256,18 +219,4 @@ module Crystal::System::User
     LibC.NetApiBufferFree(domain)
     is_domain
   end
-
-  private def self.sid_to_s(sid : LibC::SID*) : String
-    if LibC.ConvertSidToStringSidW(sid, out ptr) == 0
-      raise RuntimeError.from_winerror("ConvertSidToStringSidW")
-    end
-    str, _ = String.from_utf16(ptr)
-    LibC.LocalFree(ptr)
-    str
-  end
-
-  private def self.sid_from_s(str : String) : LibC::SID*
-    status = LibC.ConvertStringSidToSidW(Crystal::System.to_wstr(str), out sid)
-    status != 0 ? sid : Pointer(LibC::SID).null
-  end
 end
diff --git a/src/crystal/system/windows.cr b/src/crystal/system/windows.cr
index b303d4d61f6d..90b38396cf8f 100644
--- a/src/crystal/system/windows.cr
+++ b/src/crystal/system/windows.cr
@@ -1,3 +1,5 @@
+require "c/sddl"
+
 # :nodoc:
 module Crystal::System
   def self.retry_wstr_buffer(&)
@@ -13,4 +15,55 @@ module Crystal::System
   def self.to_wstr(str : String, name : String? = nil) : LibC::LPWSTR
     str.check_no_null_byte(name).to_utf16.to_unsafe
   end
+
+  def self.sid_to_s(sid : LibC::SID*) : String
+    if LibC.ConvertSidToStringSidW(sid, out ptr) == 0
+      raise RuntimeError.from_winerror("ConvertSidToStringSidW")
+    end
+    str, _ = String.from_utf16(ptr)
+    LibC.LocalFree(ptr)
+    str
+  end
+
+  def self.sid_from_s(str : String) : LibC::SID*
+    status = LibC.ConvertStringSidToSidW(to_wstr(str), out sid)
+    status != 0 ? sid : Pointer(LibC::SID).null
+  end
+
+  record SIDLookupResult, sid : LibC::SID*, domain : String, type : LibC::SID_NAME_USE
+
+  def self.name_to_sid(name : String) : SIDLookupResult?
+    utf16_name = to_wstr(name)
+
+    sid_size = LibC::DWORD.zero
+    domain_buf_size = LibC::DWORD.zero
+    LibC.LookupAccountNameW(nil, utf16_name, nil, pointerof(sid_size), nil, pointerof(domain_buf_size), out _)
+
+    unless WinError.value.error_none_mapped?
+      sid = Pointer(UInt8).malloc(sid_size).as(LibC::SID*)
+      domain_buf = Slice(LibC::WCHAR).new(domain_buf_size)
+      if LibC.LookupAccountNameW(nil, utf16_name, sid, pointerof(sid_size), domain_buf, pointerof(domain_buf_size), out sid_type) != 0
+        domain = String.from_utf16(domain_buf[..-2])
+        SIDLookupResult.new(sid, domain, sid_type)
+      end
+    end
+  end
+
+  record NameLookupResult, name : String, domain : String, type : LibC::SID_NAME_USE
+
+  def self.sid_to_name(sid : LibC::SID*) : NameLookupResult?
+    name_buf_size = LibC::DWORD.zero
+    domain_buf_size = LibC::DWORD.zero
+    LibC.LookupAccountSidW(nil, sid, nil, pointerof(name_buf_size), nil, pointerof(domain_buf_size), out _)
+
+    unless WinError.value.error_none_mapped?
+      name_buf = Slice(LibC::WCHAR).new(name_buf_size)
+      domain_buf = Slice(LibC::WCHAR).new(domain_buf_size)
+      if LibC.LookupAccountSidW(nil, sid, name_buf, pointerof(name_buf_size), domain_buf, pointerof(domain_buf_size), out sid_type) != 0
+        name = String.from_utf16(name_buf[..-2])
+        domain = String.from_utf16(domain_buf[..-2])
+        NameLookupResult.new(name, domain, sid_type)
+      end
+    end
+  end
 end
diff --git a/src/docs_main.cr b/src/docs_main.cr
index e670d6d3fa83..ab3ee2affdbc 100644
--- a/src/docs_main.cr
+++ b/src/docs_main.cr
@@ -56,8 +56,6 @@ require "./uri/params/serializable"
 require "./uuid"
 require "./uuid/json"
 require "./syscall"
-{% unless flag?(:win32) %}
-  require "./system/*"
-{% end %}
+require "./system/*"
 require "./wait_group"
 require "./docs_pseudo_methods"