diff --git a/docs/sql-keywords.md b/docs/sql-keywords.md
index 816b4eaa0ca63..1247d6e2d5f41 100644
--- a/docs/sql-keywords.md
+++ b/docs/sql-keywords.md
@@ -273,6 +273,7 @@ Below is a list of all the keywords in Spark SQL.
   <tr><td>UNCACHE</td><td>non-reserved</td><td>non-reserved</td><td>non-reserved</td></tr>
   <tr><td>UNION</td><td>reserved</td><td>strict-non-reserved</td><td>reserved</td></tr>
   <tr><td>UNIQUE</td><td>reserved</td><td>non-reserved</td><td>reserved</td></tr>
+  <tr><td>UNKNOWN</td><td>reserved</td><td>non-reserved</td><td>reserved</td></tr>
   <tr><td>UNLOCK</td><td>non-reserved</td><td>non-reserved</td><td>non-reserved</td></tr>
   <tr><td>UNSET</td><td>non-reserved</td><td>non-reserved</td><td>non-reserved</td></tr>
   <tr><td>USE</td><td>non-reserved</td><td>non-reserved</td><td>non-reserved</td></tr>
diff --git a/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4 b/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
index a1c11504a9036..49adf86c12543 100644
--- a/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
+++ b/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
@@ -660,6 +660,7 @@ predicate
     | NOT? kind=IN '(' query ')'
     | NOT? kind=(RLIKE | LIKE) pattern=valueExpression
     | IS NOT? kind=NULL
+    | IS NOT? kind=(TRUE | FALSE | UNKNOWN)
     | IS NOT? kind=DISTINCT FROM right=valueExpression
     ;
 
@@ -1330,6 +1331,7 @@ nonReserved
     | UNBOUNDED
     | UNCACHE
     | UNIQUE
+    | UNKNOWN
     | UNLOCK
     | UNSET
     | USE
@@ -1592,6 +1594,7 @@ UNBOUNDED: 'UNBOUNDED';
 UNCACHE: 'UNCACHE';
 UNION: 'UNION';
 UNIQUE: 'UNIQUE';
+UNKNOWN: 'UNKNOWN';
 UNLOCK: 'UNLOCK';
 UNSET: 'UNSET';
 USE: 'USE';
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
index 06985ac85b70e..eb91b4c2a6fb2 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
@@ -840,3 +840,85 @@ case class GreaterThanOrEqual(left: Expression, right: Expression)
 
   protected override def nullSafeEval(input1: Any, input2: Any): Any = ordering.gteq(input1, input2)
 }
+
+trait BooleanTest extends UnaryExpression with Predicate with ExpectsInputTypes {
+
+  def boolValueForComparison: Boolean
+  def boolValueWhenNull: Boolean
+
+  override def nullable: Boolean = false
+  override def inputTypes: Seq[DataType] = Seq(BooleanType)
+
+  override def eval(input: InternalRow): Any = {
+    val value = child.eval(input)
+    Option(value) match {
+      case None => boolValueWhenNull
+      case other => if (boolValueWhenNull) {
+        value == !boolValueForComparison
+      } else {
+        value == boolValueForComparison
+      }
+    }
+  }
+
+  override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+    val eval = child.genCode(ctx)
+    ev.copy(code = code"""
+      ${eval.code}
+      ${CodeGenerator.javaType(dataType)} ${ev.value} = ${CodeGenerator.defaultValue(dataType)};
+      if (${eval.isNull}) {
+        ${ev.value} = $boolValueWhenNull;
+      } else if ($boolValueWhenNull) {
+        ${ev.value} = ${eval.value} == !$boolValueForComparison;
+      } else {
+        ${ev.value} = ${eval.value} == $boolValueForComparison;
+      }
+      """, isNull = FalseLiteral)
+  }
+}
+
+case class IsTrue(child: Expression) extends BooleanTest {
+  override def boolValueForComparison: Boolean = true
+  override def boolValueWhenNull: Boolean = false
+  override def sql: String = s"(${child.sql} IS TRUE)"
+}
+
+case class IsNotTrue(child: Expression) extends BooleanTest {
+  override def boolValueForComparison: Boolean = true
+  override def boolValueWhenNull: Boolean = true
+  override def sql: String = s"(${child.sql} IS NOT TRUE)"
+}
+
+case class IsFalse(child: Expression) extends BooleanTest {
+  override def boolValueForComparison: Boolean = false
+  override def boolValueWhenNull: Boolean = false
+  override def sql: String = s"(${child.sql} IS FALSE)"
+}
+
+case class IsNotFalse(child: Expression) extends BooleanTest {
+  override def boolValueForComparison: Boolean = false
+  override def boolValueWhenNull: Boolean = true
+  override def sql: String = s"(${child.sql} IS NOT FALSE)"
+}
+
+/**
+ * IS UNKNOWN and IS NOT UNKNOWN are the same as IS NULL and IS NOT NULL, respectively,
+ * except that the input expression must be of a boolean type.
+ */
+object IsUnknown {
+  def apply(child: Expression): Predicate = {
+    new IsNull(child) with ExpectsInputTypes {
+      override def inputTypes: Seq[DataType] = Seq(BooleanType)
+      override def sql: String = s"(${child.sql} IS UNKNOWN)"
+    }
+  }
+}
+
+object IsNotUnknown {
+  def apply(child: Expression): Predicate = {
+    new IsNotNull(child) with ExpectsInputTypes {
+      override def inputTypes: Seq[DataType] = Seq(BooleanType)
+      override def sql: String = s"(${child.sql} IS NOT UNKNOWN)"
+    }
+  }
+}
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
index 5eef8dbdfbffc..51b476a643002 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
@@ -1210,6 +1210,7 @@ class AstBuilder(conf: SQLConf) extends SqlBaseBaseVisitor[AnyRef] with Logging
    * - (NOT) LIKE
    * - (NOT) RLIKE
    * - IS (NOT) NULL.
+   * - IS (NOT) (TRUE | FALSE | UNKNOWN)
    * - IS (NOT) DISTINCT FROM
    */
   private def withPredicate(e: Expression, ctx: PredicateContext): Expression = withOrigin(ctx) {
@@ -1243,6 +1244,18 @@ class AstBuilder(conf: SQLConf) extends SqlBaseBaseVisitor[AnyRef] with Logging
         IsNotNull(e)
       case SqlBaseParser.NULL =>
         IsNull(e)
+      case SqlBaseParser.TRUE => ctx.NOT match {
+        case null => IsTrue(e)
+        case _ => IsNotTrue(e)
+      }
+      case SqlBaseParser.FALSE => ctx.NOT match {
+        case null => IsFalse(e)
+        case _ => IsNotFalse(e)
+      }
+      case SqlBaseParser.UNKNOWN => ctx.NOT match {
+        case null => IsUnknown(e)
+        case _ => IsNotUnknown(e)
+      }
       case SqlBaseParser.DISTINCT if ctx.NOT != null =>
         EqualNullSafe(e, expression(ctx.right))
       case SqlBaseParser.DISTINCT =>
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/PredicateSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/PredicateSuite.scala
index 9b6896f65abfd..7bff277c793ea 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/PredicateSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/PredicateSuite.scala
@@ -521,4 +521,43 @@ class PredicateSuite extends SparkFunSuite with ExpressionEvalHelper {
     val expected = "(('id = 1) OR ('id = 2))"
     assert(expression == expected)
   }
+
+  val row0 = create_row(null)
+  val row1 = create_row(false)
+  val row2 = create_row(true)
+
+  test("istrue and isnottrue") {
+    checkEvaluation(IsTrue(Literal.create(null, BooleanType)), false, row0)
+    checkEvaluation(IsNotTrue(Literal.create(null, BooleanType)), true, row0)
+    checkEvaluation(IsTrue(Literal.create(false, BooleanType)), false, row1)
+    checkEvaluation(IsNotTrue(Literal.create(false, BooleanType)), true, row1)
+    checkEvaluation(IsTrue(Literal.create(true, BooleanType)), true, row2)
+    checkEvaluation(IsNotTrue(Literal.create(true, BooleanType)), false, row2)
+    IsTrue(Literal.create(null, IntegerType)).checkInputDataTypes() match {
+      case TypeCheckResult.TypeCheckFailure(msg) =>
+        assert(msg.contains("argument 1 requires boolean type"))
+    }
+  }
+
+  test("isfalse and isnotfalse") {
+    checkEvaluation(IsFalse(Literal.create(null, BooleanType)), false, row0)
+    checkEvaluation(IsNotFalse(Literal.create(null, BooleanType)), true, row0)
+    checkEvaluation(IsFalse(Literal.create(false, BooleanType)), true, row1)
+    checkEvaluation(IsNotFalse(Literal.create(false, BooleanType)), false, row1)
+    checkEvaluation(IsFalse(Literal.create(true, BooleanType)), false, row2)
+    checkEvaluation(IsNotFalse(Literal.create(true, BooleanType)), true, row2)
+    IsFalse(Literal.create(null, IntegerType)).checkInputDataTypes() match {
+      case TypeCheckResult.TypeCheckFailure(msg) =>
+        assert(msg.contains("argument 1 requires boolean type"))
+    }
+  }
+
+  test("isunknown and isnotunknown") {
+    checkEvaluation(IsUnknown(Literal.create(null, BooleanType)), true, row0)
+    checkEvaluation(IsNotUnknown(Literal.create(null, BooleanType)), false, row0)
+    IsUnknown(Literal.create(null, IntegerType)).checkInputDataTypes() match {
+      case TypeCheckResult.TypeCheckFailure(msg) =>
+        assert(msg.contains("argument 1 requires boolean type"))
+    }
+  }
 }
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/TableIdentifierParserSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/TableIdentifierParserSuite.scala
index ba01380558530..f610a1be5695f 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/TableIdentifierParserSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/TableIdentifierParserSuite.scala
@@ -536,6 +536,7 @@ class TableIdentifierParserSuite extends SparkFunSuite with SQLHelper {
     "uncache",
     "union",
     "unique",
+    "unknown",
     "unlock",
     "unset",
     "use",
@@ -621,6 +622,7 @@ class TableIdentifierParserSuite extends SparkFunSuite with SQLHelper {
     "trailing",
     "union",
     "unique",
+    "unknown",
     "user",
     "using",
     "when",