diff --git a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
index a57b2ee30ac9..0617f6238285 100644
--- a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
+++ b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
@@ -42,7 +42,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val verbose: Setting[Boolean] = BooleanSetting("-verbose", "Output messages about what the compiler is doing.") withAbbreviation "--verbose"
   val version: Setting[Boolean] = BooleanSetting("-version", "Print product version and exit.") withAbbreviation "--version"
   val pageWidth: Setting[Int] = IntSetting("-pagewidth", "Set page width", 80) withAbbreviation "--page-width"
-  val language: Setting[List[String]] = MultiStringSetting("-language", "feature", "Enable one or more language features.") withAbbreviation "--language"
+  val language: Setting[List[String]] = MultiChoiceSetting("-language", "feature", "Enable one or more language features.", featureChoices) withAbbreviation "--language"
   val rewrite: Setting[Option[Rewrites]] = OptionSetting[Rewrites]("-rewrite", "When used in conjunction with a `...-migration` source version, rewrites sources to migrate to new version.") withAbbreviation "--rewrite"
   val silentWarnings: Setting[Boolean] = BooleanSetting("-nowarn", "Silence all warnings.") withAbbreviation "--no-warnings"
   val fromTasty: Setting[Boolean] = BooleanSetting("-from-tasty", "Compile classes from tasty files. The arguments are .tasty or .jar files.") withAbbreviation "--from-tasty"
@@ -225,4 +225,24 @@ class ScalaSettings extends Settings.SettingGroup {
   val docSnapshot: Setting[Boolean] = BooleanSetting("-doc-snapshot", "Generate a documentation snapshot for the current Dotty version")
 
   val wikiSyntax: Setting[Boolean] = BooleanSetting("-Xwiki-syntax", "Retains the Scala2 behavior of using Wiki Syntax in Scaladoc.")
+
+  // derive choices for -language from scala.language aka scalaShadowing.language
+  private def featureChoices: List[String] =
+    List(scalaShadowing.language.getClass, scalaShadowing.language.experimental.getClass).flatMap { cls =>
+      import java.lang.reflect.{Member, Modifier}
+      def isPublic(m: Member): Boolean = Modifier.isPublic(m.getModifiers)
+      def goodFields(nm: String): List[String] =
+        nm match {
+          case "experimental" => Nil
+          case s if s.contains("$") =>
+            val adjusted = s.replace("$u002E", ".").replace("$minus", "-")
+            if adjusted.contains("$") then Nil else adjusted :: Nil
+          case _ => nm :: Nil
+        }
+      val isX = cls.getName.contains("experimental")
+      def prefixed(nm: String) = if isX then s"experimental.$nm" else nm
+
+      cls.getDeclaredMethods.filter(isPublic).map(_.getName).map(prefixed)
+      ++ cls.getDeclaredFields.filter(isPublic).map(_.getName).flatMap(goodFields).map(prefixed)
+    }
 }
diff --git a/compiler/src/dotty/tools/dotc/config/Settings.scala b/compiler/src/dotty/tools/dotc/config/Settings.scala
index a351921e8e64..df8886a252ba 100644
--- a/compiler/src/dotty/tools/dotc/config/Settings.scala
+++ b/compiler/src/dotty/tools/dotc/config/Settings.scala
@@ -9,6 +9,7 @@ import annotation.tailrec
 import collection.mutable.ArrayBuffer
 import language.existentials
 import reflect.ClassTag
+import scala.PartialFunction.cond
 import scala.util.{Success, Failure}
 
 object Settings {
@@ -91,27 +92,16 @@ object Settings {
     def isMultivalue: Boolean = implicitly[ClassTag[T]] == ListTag
 
     def legalChoices: String =
-      choices match {
+      choices match
         case xs if xs.isEmpty => ""
         case r: Range         => s"${r.head}..${r.last}"
         case xs: List[?]      => xs.toString
-      }
 
     def isLegal(arg: Any): Boolean =
-      choices match {
-        case xs if xs.isEmpty =>
-          arg match {
-            case _: T => true
-            case _ => false
-          }
-        case r: Range =>
-          arg match {
-            case x: Int => r.head <= x && x <= r.last
-            case _ => false
-          }
-        case xs: List[?] =>
-          xs.contains(arg)
-      }
+      choices match
+        case xs if xs.isEmpty => cond(arg) { case _: T => true }
+        case r: Range         => cond(arg) { case x: Int => r.head <= x && x <= r.last }
+        case xs: List[?]      => xs.contains(arg)
 
     def tryToSet(state: ArgsSummary): ArgsSummary = {
       val ArgsSummary(sstate, arg :: args, errors, warnings) = state
@@ -132,14 +122,21 @@ object Settings {
         ArgsSummary(sstate, args, errors :+ msg, warnings)
       def missingArg =
         fail(s"missing argument for option $name", args)
-      def doSet(argRest: String) = ((implicitly[ClassTag[T]], args): @unchecked) match {
+      def doSet(argRest: String) = ((implicitly[ClassTag[T]], args): @unchecked) match
         case (BooleanTag, _) =>
           update(true, args)
         case (OptionTag, _) =>
           update(Some(propertyClass.get.getConstructor().newInstance()), args)
+        case (ListTag, _) if argRest.isEmpty =>
+          missingArg
+        case (ListTag, _) if choices.nonEmpty =>
+          val ss = argRest.split(",").toList
+          ss.find(s => !choices.exists(c => c.asInstanceOf[List[String]].contains(s))) match {
+            case Some(s) => fail(s"$s is not a valid choice for $name", args)
+            case None    => update(ss, args)
+          }
         case (ListTag, _) =>
-          if (argRest.isEmpty) missingArg
-          else update((argRest split ",").toList, args)
+          update((argRest split ",").toList, args)
         case (StringTag, _) if choices.nonEmpty && argRest.nonEmpty =>
           if (!choices.contains(argRest))
             fail(s"$arg is not a valid choice for $name", args)
@@ -177,7 +174,7 @@ object Settings {
           }
         case (_, Nil) =>
           missingArg
-      }
+      end doSet
 
       if (prefix != "" && arg.startsWith(prefix))
         doSet(arg drop prefix.length)
@@ -278,6 +275,9 @@ object Settings {
     def IntSetting(name: String, descr: String, default: Int, range: Seq[Int] = Nil): Setting[Int] =
       publish(Setting(name, descr, default, choices = range))
 
+    def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String]): Setting[List[String]] =
+      publish(Setting(name, descr, Nil, helpArg, choices.map(c => List(c))))
+
     def MultiStringSetting(name: String, helpArg: String, descr: String): Setting[List[String]] =
       publish(Setting(name, descr, Nil, helpArg))
 
diff --git a/compiler/test/dotty/tools/dotc/CompilationTests.scala b/compiler/test/dotty/tools/dotc/CompilationTests.scala
index c7813a86e243..fd619b079e3e 100644
--- a/compiler/test/dotty/tools/dotc/CompilationTests.scala
+++ b/compiler/test/dotty/tools/dotc/CompilationTests.scala
@@ -158,7 +158,8 @@ class CompilationTests {
       compileFile("tests/neg-custom-args/indentRight.scala", defaultOptions.and("-noindent", "-Xfatal-warnings")),
       compileFile("tests/neg-custom-args/extmethods-tparams.scala", defaultOptions.and("-deprecation", "-Xfatal-warnings")),
       compileDir("tests/neg-custom-args/adhoc-extension", defaultOptions.and("-source", "3.1", "-feature", "-Xfatal-warnings")),
-      compileFile("tests/neg/i7575.scala", defaultOptions.withoutLanguageFeatures.and("-language:_")),
+      compileFile("tests/neg/i7575.scala", defaultOptions.withoutLanguageFeatures),
+      compileFile("tests/neg-custom-args/i7575c.scala", defaultOptions.and("-language:_")),
       compileFile("tests/neg-custom-args/kind-projector.scala", defaultOptions.and("-Ykind-projector")),
       compileFile("tests/neg-custom-args/typeclass-derivation2.scala", defaultOptions.and("-Yerased-terms")),
       compileFile("tests/neg-custom-args/i5498-postfixOps.scala", defaultOptions withoutLanguageFeature "postfixOps"),
diff --git a/compiler/test/dotty/tools/dotc/SettingsTests.scala b/compiler/test/dotty/tools/dotc/SettingsTests.scala
index f0e1699358b2..969264abc211 100644
--- a/compiler/test/dotty/tools/dotc/SettingsTests.scala
+++ b/compiler/test/dotty/tools/dotc/SettingsTests.scala
@@ -37,4 +37,28 @@ class SettingsTests {
     val options  = Array("-encoding", "-d", outputDir.toString, source.toString)
     val reporter = Main.process(options, reporter = StoreReporter())
     assertEquals(1, reporter.errorCount)
+
+  //List(dynamics, existentials, higherKinds, implicitConversions, postfixOps, reflectiveCalls, Scala2Compat, noAutoTupling, strictEquality, adhocExtensions, dependent, 3.0-migration, 3.0, 3.1-migration, 3.1, experimental.macros, experimental.dependent)
+  @Test def `t9901 Settings detects available language features`: Unit =
+    val options = Array("-language:dynamics,strictEquality,experimental.macros")
+    val reporter = Main.process(options, reporter = StoreReporter())
+    assertEquals(0, reporter.errorCount)
+
+  @Test def `t9901 Settings detects one erroneous language feature`: Unit =
+    val options = Array("-language:dynamics,awesome,experimental")
+    val reporter = Main.process(options, reporter = StoreReporter())
+    assertEquals(1, reporter.errorCount)
+    assertEquals("awesome is not a valid choice for -language", reporter.allErrors.head.message)
+
+  @Test def `t9901 Settings excludes experimental`: Unit =
+    val options = Array("-language:dynamics,experimental")
+    val reporter = Main.process(options, reporter = StoreReporter())
+    assertEquals(1, reporter.errorCount)
+    assertEquals("experimental is not a valid choice for -language", reporter.allErrors.head.message)
+
+  @Test def `t9901 Settings includes funky strings`: Unit =
+    val options = Array("-language:3.1-migration")
+    val reporter = Main.process(options, reporter = StoreReporter())
+    assertEquals(0, reporter.errorCount)
+
 }
diff --git a/compiler/test/dotty/tools/dotc/config/ScalaSettingsTests.scala b/compiler/test/dotty/tools/dotc/config/ScalaSettingsTests.scala
index 60c4bfa57fc1..d1fccfc6c286 100644
--- a/compiler/test/dotty/tools/dotc/config/ScalaSettingsTests.scala
+++ b/compiler/test/dotty/tools/dotc/config/ScalaSettingsTests.scala
@@ -51,4 +51,32 @@ class ScalaSettingsTests:
     assertTrue("Has the feature", set.contains("implicitConversions"))
     assertTrue("Has the feature", set.contains("dynamics"))
 
+  @Test def `A multichoice setting is multivalued`: Unit =
+    class SUT extends SettingGroup:
+      val language: Setting[List[String]] = MultiChoiceSetting("-language", "feature", "Enable creature features.", List("foo", "bar", "baz"))
+    val sut  = SUT()
+    val args = tokenize("-language:foo,baz")
+    val sumy = ArgsSummary(sut.defaultState, args, errors = Nil, warnings = Nil)
+    val res  = sut.processArguments(sumy, processAll = true, skipped = Nil)
+    val set  = sut.language.valueIn(res.sstate)
+    assertEquals(1, args.length)
+    assertTrue("No warnings!", res.warnings.isEmpty)
+    assertTrue("No errors!", res.errors.isEmpty)
+    assertTrue("Has the feature", set.contains("foo"))
+    assertTrue("Has the feature", set.contains("baz"))
+
+  @Test def `A multichoice setting is restricted`: Unit =
+    class SUT extends SettingGroup:
+      val language: Setting[List[String]] = MultiChoiceSetting("-language", "feature", "Enable creature features.", List("foo", "bar", "baz"))
+    val sut  = SUT()
+    val args = tokenize("-language:foo,bah")
+    val sumy = ArgsSummary(sut.defaultState, args, errors = Nil, warnings = Nil)
+    val res  = sut.processArguments(sumy, processAll = true, skipped = Nil)
+    val set  = sut.language.valueIn(res.sstate)
+    assertEquals(1, args.length)
+    assertTrue("No warnings!", res.warnings.isEmpty)
+    assertEquals(1, res.errors.size)
+    assertFalse("Has the foo feature", set.contains("foo"))
+    assertFalse("Has the bah feature", set.contains("bah"))
+
 end ScalaSettingsTests
diff --git a/tests/neg-custom-args/i7575c.scala b/tests/neg-custom-args/i7575c.scala
new file mode 100644
index 000000000000..ed5b51df6ec8
--- /dev/null
+++ b/tests/neg-custom-args/i7575c.scala
@@ -0,0 +1,3 @@
+// tested with -language:_, which is illegal
+// nopos-error
+class C