diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfiguration.java b/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfiguration.java
index bd68b48e3e91c6..48753eff9a8600 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfiguration.java
@@ -29,7 +29,7 @@ public class PlatformConfiguration extends BuildConfiguration.Fragment
     implements PlatformConfigurationApi {
   private final Label hostPlatform;
   private final ImmutableList<String> extraExecutionPlatforms;
-  private final ImmutableList<Label> targetPlatforms;
+  private final Label targetPlatform;
   private final ImmutableList<String> extraToolchains;
   private final ImmutableList<Label> enabledToolchainTypes;
 
@@ -37,12 +37,12 @@ public class PlatformConfiguration extends BuildConfiguration.Fragment
   PlatformConfiguration(
       Label hostPlatform,
       ImmutableList<String> extraExecutionPlatforms,
-      ImmutableList<Label> targetPlatforms,
+      Label targetPlatform,
       ImmutableList<String> extraToolchains,
       ImmutableList<Label> enabledToolchainTypes) {
     this.hostPlatform = hostPlatform;
     this.extraExecutionPlatforms = extraExecutionPlatforms;
-    this.targetPlatforms = targetPlatforms;
+    this.targetPlatform = targetPlatform;
     this.extraToolchains = extraToolchains;
     this.enabledToolchainTypes = enabledToolchainTypes;
   }
@@ -60,9 +60,19 @@ public ImmutableList<String> getExtraExecutionPlatforms() {
     return extraExecutionPlatforms;
   }
 
+  /**
+   * Returns the single target platform used in this configuration. The flag is multi-valued for
+   * future handling of multiple target platforms but any given configuration should only be
+   * concerned with a single target platform.
+   */
+  @Override
+  public Label getTargetPlatform() {
+    return targetPlatform;
+  }
+
   @Override
   public ImmutableList<Label> getTargetPlatforms() {
-    return targetPlatforms;
+    return ImmutableList.of(targetPlatform);
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfigurationLoader.java b/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfigurationLoader.java
index 6239aca9c7e944..4473c941d5793b 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfigurationLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/PlatformConfigurationLoader.java
@@ -16,12 +16,14 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.analysis.config.BuildOptions;
 import com.google.devtools.build.lib.analysis.config.ConfigurationEnvironment;
 import com.google.devtools.build.lib.analysis.config.ConfigurationFragmentFactory;
 import com.google.devtools.build.lib.analysis.config.FragmentOptions;
 import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
+import com.google.devtools.build.lib.cmdline.Label;
 
 /** A loader that creates {@link PlatformConfiguration} instances based on command-line options. */
 public class PlatformConfigurationLoader implements ConfigurationFragmentFactory {
@@ -44,10 +46,18 @@ public Class<? extends BuildConfiguration.Fragment> creates() {
 
   private PlatformConfiguration create(PlatformOptions options)
       throws InvalidConfigurationException {
+
+    if (options.hostPlatform == null) {
+      throw new InvalidConfigurationException("Host platform not set");
+    }
+    Label targetPlatform = Iterables.getFirst(options.platforms, null);
+    if (targetPlatform == null) {
+      throw new InvalidConfigurationException("Target platform not set");
+    }
     return new PlatformConfiguration(
         options.hostPlatform,
         ImmutableList.copyOf(options.extraExecutionPlatforms),
-        ImmutableList.copyOf(options.platforms),
+        targetPlatform,
         ImmutableList.copyOf(options.extraToolchains),
         ImmutableList.copyOf(options.enabledToolchainTypes));
   }
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ToolchainUtil.java b/src/main/java/com/google/devtools/build/lib/skyframe/ToolchainUtil.java
index 5b5a92e9795eb1..8399fb783b30e8 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ToolchainUtil.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ToolchainUtil.java
@@ -103,7 +103,7 @@ static ToolchainContext createToolchainContext(
       return null;
     }
     Label hostPlatformLabel = platformConfiguration.getHostPlatform();
-    Label targetPlatformLabel = platformConfiguration.getTargetPlatforms().get(0);
+    Label targetPlatformLabel = platformConfiguration.getTargetPlatform();
 
     ConfiguredTargetKey hostPlatformKey = ConfiguredTargetKey.of(hostPlatformLabel, configuration);
     ConfiguredTargetKey targetPlatformKey =
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/PlatformConfigurationApi.java b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/PlatformConfigurationApi.java
index be7b8315481ab6..06841e91cbc351 100644
--- a/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/PlatformConfigurationApi.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/PlatformConfigurationApi.java
@@ -32,15 +32,22 @@
 public interface PlatformConfigurationApi {
 
   @SkylarkCallable(name = "host_platform", structField = true, doc = "The current host platform")
-  public Label getHostPlatform();
+  Label getHostPlatform();
 
-  @SkylarkCallable(name = "platforms", structField = true, doc = "The current target platforms")
-  public ImmutableList<Label> getTargetPlatforms();
+  @SkylarkCallable(name = "platform", structField = true, doc = "The current target platform")
+  Label getTargetPlatform();
 
   @SkylarkCallable(
-    name = "enabled_toolchain_types",
-    structField = true,
-    doc = "The set of toolchain types enabled for platform-based toolchain selection."
-  )
-  public List<Label> getEnabledToolchainTypes();
+      name = "platforms",
+      structField = true,
+      doc = "The current target platforms",
+      documented = false)
+  @Deprecated
+  ImmutableList<Label> getTargetPlatforms();
+
+  @SkylarkCallable(
+      name = "enabled_toolchain_types",
+      structField = true,
+      doc = "The set of toolchain types enabled for platform-based toolchain selection.")
+  List<Label> getEnabledToolchainTypes();
 }
diff --git a/src/test/java/com/google/devtools/build/lib/rules/platform/BUILD b/src/test/java/com/google/devtools/build/lib/rules/platform/BUILD
index 704fcb4ea2abcc..6b69d171d2d8cf 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/platform/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/rules/platform/BUILD
@@ -12,36 +12,35 @@ filegroup(
 
 TESTUTIL_SRCS = ["ToolchainTestCase.java"]
 
-java_test(
-    name = "PlatformRulesTests",
+java_library(
+    name = "PlatformRulesTests_lib",
     srcs = glob(
         ["*.java"],
         exclude = TESTUTIL_SRCS,
     ),
-    test_class = "com.google.devtools.build.lib.AllTests",
     deps = [
         "//src/main/java/com/google/devtools/build/lib:build-base",
-        "//src/main/java/com/google/devtools/build/lib:os_util",
         "//src/main/java/com/google/devtools/build/lib:packages-internal",
-        "//src/main/java/com/google/devtools/build/lib:syntax",
-        "//src/main/java/com/google/devtools/build/lib:util",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform:utils",
-        "//src/main/java/com/google/devtools/build/lib/cmdline",
-        "//src/main/java/com/google/devtools/build/lib/collect",
-        "//src/main/java/com/google/devtools/build/skyframe",
-        "//src/main/java/com/google/devtools/build/skyframe:skyframe-objects",
+        "//src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform",
         "//src/test/java/com/google/devtools/build/lib:analysis_testutil",
-        "//src/test/java/com/google/devtools/build/lib:packages_testutil",
-        "//src/test/java/com/google/devtools/build/lib/skyframe:testutil",
-        "//src/test/java/com/google/devtools/build/lib/skylark:testutil",
+        "//src/test/java/com/google/devtools/build/lib:testutil",
         "//third_party:guava",
-        "//third_party:guava-testlib",
         "//third_party:junit4",
         "//third_party:truth",
     ],
 )
 
+java_test(
+    name = "PlatformRulesTests",
+    test_class = "com.google.devtools.build.lib.AllTests",
+    runtime_deps = [
+        ":PlatformRulesTests_lib",
+        "//src/test/java/com/google/devtools/build/lib:test_runner",
+    ],
+)
+
 java_library(
     name = "testutil",
     srcs = TESTUTIL_SRCS,
diff --git a/src/test/java/com/google/devtools/build/lib/rules/platform/PlatformConfigurationApiTest.java b/src/test/java/com/google/devtools/build/lib/rules/platform/PlatformConfigurationApiTest.java
new file mode 100644
index 00000000000000..07c5462a123002
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/rules/platform/PlatformConfigurationApiTest.java
@@ -0,0 +1,173 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.lib.rules.platform;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
+import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.packages.SkylarkProvider.SkylarkKey;
+import com.google.devtools.build.lib.packages.StructImpl;
+import com.google.devtools.build.lib.skylarkbuildapi.platform.PlatformConfigurationApi;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests Skylark API for Platform configuration fragments. */
+@RunWith(JUnit4.class)
+public class PlatformConfigurationApiTest extends BuildViewTestCase {
+
+  @Test
+  public void testHostPlatform() throws Exception {
+    scratch.file("platforms/BUILD", "platform(name = 'test_platform')");
+
+    useConfiguration("--host_platform=//platforms:test_platform");
+    ruleBuilder().build();
+    scratch.file(
+        "foo/BUILD",
+        "load(':extension.bzl', 'my_rule')",
+        "my_rule(",
+        "  name = 'my_skylark_rule',",
+        ")");
+    assertNoEvents();
+
+    PlatformConfigurationApi platformConfiguration = fetchPlatformConfiguration();
+    assertThat(platformConfiguration).isNotNull();
+    assertThat(platformConfiguration.getHostPlatform())
+        .isEqualTo(Label.parseAbsoluteUnchecked("//platforms:test_platform"));
+  }
+
+  @Test
+  public void testHostPlatform_unset() {
+    assertThrows(InvalidConfigurationException.class, () -> useConfiguration("--host_platform="));
+  }
+
+  @Test
+  public void testTargetPlatform_single() throws Exception {
+    scratch.file("platforms/BUILD", "platform(name = 'test_platform')");
+
+    useConfiguration("--platforms=//platforms:test_platform");
+    ruleBuilder().build();
+    scratch.file(
+        "foo/BUILD",
+        "load(':extension.bzl', 'my_rule')",
+        "my_rule(",
+        "  name = 'my_skylark_rule',",
+        ")");
+    assertNoEvents();
+
+    PlatformConfigurationApi platformConfiguration = fetchPlatformConfiguration();
+    assertThat(platformConfiguration).isNotNull();
+    assertThat(platformConfiguration.getTargetPlatform())
+        .isEqualTo(Label.parseAbsoluteUnchecked("//platforms:test_platform"));
+    assertThat(platformConfiguration.getTargetPlatforms())
+        .containsExactly(Label.parseAbsoluteUnchecked("//platforms:test_platform"));
+  }
+
+  @Test
+  public void testTargetPlatform_unset() {
+    assertThrows(InvalidConfigurationException.class, () -> useConfiguration("--platforms="));
+  }
+
+  @Test
+  public void testTargetPlatform_multiple() throws Exception {
+    scratch.file(
+        "platforms/BUILD",
+        "platform(name = 'test_platform1')",
+        "platform(name = 'test_platform2')");
+
+    useConfiguration("--platforms=//platforms:test_platform1,//platforms:test_platform2");
+    ruleBuilder().build();
+    scratch.file(
+        "foo/BUILD",
+        "load(':extension.bzl', 'my_rule')",
+        "my_rule(",
+        "  name = 'my_skylark_rule',",
+        ")");
+    assertNoEvents();
+
+    PlatformConfigurationApi platformConfiguration = fetchPlatformConfiguration();
+    assertThat(platformConfiguration).isNotNull();
+    // Despite setting two platforms in the flag, only a single platform should be visible to the
+    // target.
+    assertThat(platformConfiguration.getTargetPlatform())
+        .isEqualTo(Label.parseAbsoluteUnchecked("//platforms:test_platform1"));
+    assertThat(platformConfiguration.getTargetPlatforms())
+        .containsExactly(Label.parseAbsoluteUnchecked("//platforms:test_platform1"));
+  }
+
+  @Test
+  public void testEnabledToolchainTypes() throws Exception {
+    scratch.file(
+        "toolchains/BUILD",
+        "toolchain_type(name = 'test_toolchain_type1')",
+        "toolchain_type(name = 'test_toolchain_type2')",
+        "toolchain_type(name = 'test_toolchain_type3')");
+
+    useConfiguration(
+        "--enabled_toolchain_types="
+            + "//toolchains:test_toolchain_type1,//toolchains:test_toolchain_type3");
+    ruleBuilder().build();
+    scratch.file(
+        "foo/BUILD",
+        "load(':extension.bzl', 'my_rule')",
+        "my_rule(",
+        "  name = 'my_skylark_rule',",
+        ")");
+    assertNoEvents();
+
+    PlatformConfigurationApi platformConfiguration = fetchPlatformConfiguration();
+    assertThat(platformConfiguration).isNotNull();
+    assertThat(platformConfiguration.getEnabledToolchainTypes())
+        .containsExactly(
+            Label.parseAbsoluteUnchecked("//toolchains:test_toolchain_type1"),
+            Label.parseAbsoluteUnchecked("//toolchains:test_toolchain_type3"));
+  }
+
+  private RuleBuilder ruleBuilder() {
+    return new RuleBuilder();
+  }
+
+  private class RuleBuilder {
+    private void build() throws Exception {
+      ImmutableList.Builder<String> lines = ImmutableList.builder();
+      lines.add(
+          "result = provider()",
+          "def _impl(ctx):",
+          "  platformConfig = ctx.fragments.platform",
+          "  return [result(property = platformConfig)]");
+      lines.add("my_rule = rule(", "  implementation = _impl,", "  fragments = ['platform'],", ")");
+
+      scratch.file("foo/extension.bzl", lines.build().toArray(new String[] {}));
+    }
+  }
+
+  private PlatformConfigurationApi fetchPlatformConfiguration() throws Exception {
+    ConfiguredTarget myRuleTarget = getConfiguredTarget("//foo:my_skylark_rule");
+    StructImpl info =
+        (StructImpl)
+            myRuleTarget.get(
+                new SkylarkKey(
+                    Label.parseAbsolute("//foo:extension.bzl", ImmutableMap.of()), "result"));
+
+    @SuppressWarnings("unchecked")
+    PlatformConfigurationApi javaInfo = (PlatformConfigurationApi) info.getValue("property");
+    return javaInfo;
+  }
+}