diff --git a/config/BUILDCONFIG.gn b/config/BUILDCONFIG.gn
index 59c3a0772..83c375ade 100644
--- a/config/BUILDCONFIG.gn
+++ b/config/BUILDCONFIG.gn
@@ -456,7 +456,10 @@ if (is_win) {
 } else if (is_linux) {
   host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
   set_default_toolchain("//build/toolchain/linux:$cpu_arch")
-} else if (is_mac || is_ios) {
+} else if (is_mac) {
   host_toolchain = "//build/toolchain/mac:clang"
   set_default_toolchain(host_toolchain)
+} else if (is_ios) {
+  host_toolchain = "//build/toolchain/mac:host_clang"
+  set_default_toolchain("//build/toolchain/mac:clang")
 }
diff --git a/toolchain/mac/BUILD.gn b/toolchain/mac/BUILD.gn
index 1ff00b22e..afd09e0a4 100644
--- a/toolchain/mac/BUILD.gn
+++ b/toolchain/mac/BUILD.gn
@@ -53,68 +53,87 @@ gyp_mac_tool_source =
   rebase_path("//tools/gyp/pylib/gyp/mac_tool.py", ".", root_build_dir)
 exec_script("setup_toolchain.py", [ gyp_mac_tool_source ], "value")
 
-toolchain("clang") {
-  # Make these apply to all tools below.
-  lib_prefix = "-l"
-  lib_dir_prefix="-L"
+# Shared toolchain definition. Invocations should set toolchain_os to set the
+# build args in this definition.
+template("mac_clang_toolchain") {
+  toolchain(target_name) {
+    # Make these apply to all tools below.
+    lib_prefix = "-l"
+    lib_dir_prefix="-L"
 
-  tool("cc") {
-    command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c \$cflags_pch_c -c \$in -o \$out"
-    description = "CC \$out"
-    depfile = "\$out.d"
-    deps = "gcc"
-  }
-  tool("cxx") {
-    command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc \$cflags_pch_cc -c \$in -o \$out"
-    description = "CXX \$out"
-    depfile = "\$out.d"
-    deps = "gcc"
-  }
-  tool("objc") {
-    command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c \$cflags_objc \$cflags_pch_objc -c \$in -o \$out"
-    description = "OBJC \$out"
-    depfile = "\$out.d"
-    deps = "gcc"
-  }
-  tool("objcxx") {
-    command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc \$cflags_objcc \$cflags_pch_objcc -c \$in -o \$out"
-    description = "OBJCXX \$out"
-    depfile = "\$out.d"
-    deps = "gcc"
-  }
-  tool("alink") {
-    command = "rm -f \$out && ./gyp-mac-tool filter-libtool libtool \$libtool_flags -static -o \$out \$in \$postbuilds"
-    description = "LIBTOOL-STATIC \$out, POSTBUILDS"
-  }
-  tool("solink") {
-    command = "if [ ! -e \$lib -o ! -e \${lib}.TOC ] || otool -l \$lib | grep -q LC_REEXPORT_DYLIB ; then $ld -shared \$ldflags -o \$lib \$in \$solibs \$libs \$postbuilds && { otool -l \$lib | grep LC_ID_DYLIB -A 5; nm -gP \$lib | cut -f1-2 -d' ' | grep -v U\$\$; true; } > \${lib}.TOC; else $ld -shared \$ldflags -o \$lib \$in \$solibs \$libs \$postbuilds && { otool -l \$lib | grep LC_ID_DYLIB -A 5; nm -gP \$lib | cut -f1-2 -d' ' | grep -v U\$\$; true; } > \${lib}.tmp && if ! cmp -s \${lib}.tmp \${lib}.TOC; then mv \${lib}.tmp \${lib}.TOC ; fi; fi"
-    description = "SOLINK \$lib, POSTBUILDS"
-    #pool = "link_pool"
-    restat = "1"
-  }
-  tool("link") {
-    command = "$ld \$ldflags -o \$out \$in \$solibs \$libs \$postbuilds"
-    description = "LINK \$out, POSTBUILDS"
-    #pool = "link_pool"
-  }
-  #tool("infoplist") {
-  #  command = "$cc -E -P -Wno-trigraphs -x c \$defines \$in -o \$out && plutil -convert xml1 \$out \$out"
-  #  description = "INFOPLIST \$out"
-  #}
-  #tool("mac_tool") {
-  #  command = "\$env ./gyp-mac-tool \$mactool_cmd \$in \$out"
-  #  description = "MACTOOL \$mactool_cmd \$in"
-  #}
-  #tool("package_framework") {
-  #  command = "./gyp-mac-tool package-framework \$out \$version \$postbuilds && touch \$out"
-  #  description = "PACKAGE FRAMEWORK \$out, POSTBUILDS"
-  #}
-  tool("stamp") {
-    command = "\${postbuilds}touch \$out"
-    description = "STAMP \$out"
-  }
-  tool("copy") {
-    command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
-    description = "COPY \$in \$out"
+    tool("cc") {
+      command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c \$cflags_pch_c -c \$in -o \$out"
+      description = "CC \$out"
+      depfile = "\$out.d"
+      deps = "gcc"
+    }
+    tool("cxx") {
+      command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc \$cflags_pch_cc -c \$in -o \$out"
+      description = "CXX \$out"
+      depfile = "\$out.d"
+      deps = "gcc"
+    }
+    tool("objc") {
+      command = "$cc -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_c \$cflags_objc \$cflags_pch_objc -c \$in -o \$out"
+      description = "OBJC \$out"
+      depfile = "\$out.d"
+      deps = "gcc"
+    }
+    tool("objcxx") {
+      command = "$cxx -MMD -MF \$out.d \$defines \$includes \$cflags \$cflags_cc \$cflags_objcc \$cflags_pch_objcc -c \$in -o \$out"
+      description = "OBJCXX \$out"
+      depfile = "\$out.d"
+      deps = "gcc"
+    }
+    tool("alink") {
+      command = "rm -f \$out && ./gyp-mac-tool filter-libtool libtool \$libtool_flags -static -o \$out \$in \$postbuilds"
+      description = "LIBTOOL-STATIC \$out, POSTBUILDS"
+    }
+    tool("solink") {
+      command = "if [ ! -e \$lib -o ! -e \${lib}.TOC ] || otool -l \$lib | grep -q LC_REEXPORT_DYLIB ; then $ld -shared \$ldflags -o \$lib \$in \$solibs \$libs \$postbuilds && { otool -l \$lib | grep LC_ID_DYLIB -A 5; nm -gP \$lib | cut -f1-2 -d' ' | grep -v U\$\$; true; } > \${lib}.TOC; else $ld -shared \$ldflags -o \$lib \$in \$solibs \$libs \$postbuilds && { otool -l \$lib | grep LC_ID_DYLIB -A 5; nm -gP \$lib | cut -f1-2 -d' ' | grep -v U\$\$; true; } > \${lib}.tmp && if ! cmp -s \${lib}.tmp \${lib}.TOC; then mv \${lib}.tmp \${lib}.TOC ; fi; fi"
+      description = "SOLINK \$lib, POSTBUILDS"
+      #pool = "link_pool"
+      restat = "1"
+    }
+    tool("link") {
+      command = "$ld \$ldflags -o \$out \$in \$solibs \$libs \$postbuilds"
+      description = "LINK \$out, POSTBUILDS"
+      #pool = "link_pool"
+    }
+    #tool("infoplist") {
+    #  command = "$cc -E -P -Wno-trigraphs -x c \$defines \$in -o \$out && plutil -convert xml1 \$out \$out"
+    #  description = "INFOPLIST \$out"
+    #}
+    #tool("mac_tool") {
+    #  command = "\$env ./gyp-mac-tool \$mactool_cmd \$in \$out"
+    #  description = "MACTOOL \$mactool_cmd \$in"
+    #}
+    #tool("package_framework") {
+    #  command = "./gyp-mac-tool package-framework \$out \$version \$postbuilds && touch \$out"
+    #  description = "PACKAGE FRAMEWORK \$out, POSTBUILDS"
+    #}
+    tool("stamp") {
+      command = "\${postbuilds}touch \$out"
+      description = "STAMP \$out"
+    }
+    tool("copy") {
+      command = "ln -f \$in \$out 2>/dev/null || (rm -rf \$out && cp -af \$in \$out)"
+      description = "COPY \$in \$out"
+    }
+
+    toolchain_args() {
+      os = toolchain_os
+    }
   }
 }
+
+# Toolchain representing the target build (either mac or iOS).
+mac_clang_toolchain("clang") {
+  toolchain_os = os
+}
+
+# This toolchain provides a way for iOS target compiles to reference targets
+# compiled for the host system. It just overrides the OS back to "mac".
+mac_clang_toolchain("host_clang") {
+  toolchain_os = "mac"
+}