diff --git a/build.gradle b/build.gradle
index 70bb400b3..488b35555 100644
--- a/build.gradle
+++ b/build.gradle
@@ -75,7 +75,7 @@ subprojects {
 
 javaVersions {
     libraryTarget = 17
-    runtime = 21
+    runtime = 23
 }
 
 jdks {
diff --git a/palantir-java-format-spi/build.gradle b/palantir-java-format-spi/build.gradle
index a3f1583fd..ba8daac9a 100644
--- a/palantir-java-format-spi/build.gradle
+++ b/palantir-java-format-spi/build.gradle
@@ -18,5 +18,5 @@ tasks.withType(JavaCompile).named('compileJava') {
 }
 
 javaVersion {
-    target = 21
+    target = 23
 }
diff --git a/palantir-java-format/build.gradle b/palantir-java-format/build.gradle
index 470e5cbaf..51b37e3f9 100644
--- a/palantir-java-format/build.gradle
+++ b/palantir-java-format/build.gradle
@@ -41,6 +41,16 @@ moduleJvmArgs {
             'jdk.compiler/com.sun.tools.javac.api')
 }
 
+applicationDefaultJvmArgs = [
+        '--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED',
+        '--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED'
+]
+
 tasks.withType(JavaCompile).named('compileJava') {
     // By setting the source and target compatibility to 11, while still using a higher level
     // JDK for compilation, we can compile against the AST classes we need to support >11 source
@@ -62,5 +72,5 @@ tasks.named("test") {
 }
 
 javaVersion {
-    target = 21
+    target = 23
 }
diff --git a/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavacTokens.java b/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavacTokens.java
index 705837412..eaf19fd9a 100644
--- a/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavacTokens.java
+++ b/palantir-java-format/src/main/java/com/palantir/javaformat/java/JavacTokens.java
@@ -27,7 +27,9 @@
 import com.sun.tools.javac.parser.Tokens.TokenKind;
 import com.sun.tools.javac.parser.UnicodeReader;
 import com.sun.tools.javac.util.Context;
+import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 /** A wrapper around javac's lexer. */
 class JavacTokens {
@@ -178,6 +180,12 @@ public int getSourcePos(int index) {
             return pos + index;
         }
 
+        @Override
+        @Nullable
+        public DiagnosticPosition getPos() {
+            return null;
+        }
+
         @Override
         public CommentStyle getStyle() {
             return style;
diff --git a/palantir-java-format/src/main/java/com/palantir/javaformat/java/RemoveUnusedImports.java b/palantir-java-format/src/main/java/com/palantir/javaformat/java/RemoveUnusedImports.java
index a66b6b559..15c6b652e 100644
--- a/palantir-java-format/src/main/java/com/palantir/javaformat/java/RemoveUnusedImports.java
+++ b/palantir-java-format/src/main/java/com/palantir/javaformat/java/RemoveUnusedImports.java
@@ -226,7 +226,12 @@ private static RangeMap<Integer, String> buildReplacements(
             Set<String> usedNames,
             Multimap<String, Range<Integer>> usedInJavadoc) {
         RangeMap<Integer, String> replacements = TreeRangeMap.create();
-        for (JCImport importTree : unit.getImports()) {
+        for (Object o : unit.getImports()) {
+            if (!(o instanceof JCImport)) {
+                // TODO: In Java >=23, getImports() returns JCImportBase
+                continue;
+            }
+            JCImport importTree = (JCImport) o;
             String simpleName = getSimpleName(importTree);
             if (!isUnused(unit, usedNames, usedInJavadoc, importTree, simpleName)) {
                 continue;
diff --git a/palantir-java-format/src/main/java/com/palantir/javaformat/java/java21/Java21InputAstVisitor.java b/palantir-java-format/src/main/java/com/palantir/javaformat/java/java21/Java21InputAstVisitor.java
index 5f089c4e6..6deadf1f2 100644
--- a/palantir-java-format/src/main/java/com/palantir/javaformat/java/java21/Java21InputAstVisitor.java
+++ b/palantir-java-format/src/main/java/com/palantir/javaformat/java/java21/Java21InputAstVisitor.java
@@ -18,6 +18,7 @@
 
 import com.palantir.javaformat.OpsBuilder;
 import com.palantir.javaformat.java.java14.Java14InputAstVisitor;
+import com.sun.source.tree.AnyPatternTree;
 import com.sun.source.tree.CaseTree;
 import com.sun.source.tree.ConstantCaseLabelTree;
 import com.sun.source.tree.DeconstructionPatternTree;
@@ -88,4 +89,10 @@ protected void variableName(Name name) {
             visit(name);
         }
     }
+
+    @Override
+    public Void visitAnyPattern(AnyPatternTree node, Void unused) {
+        token("_");
+        return null;
+    }
 }
diff --git a/palantir-java-format/src/test/java/com/palantir/javaformat/java/FileBasedTests.java b/palantir-java-format/src/test/java/com/palantir/javaformat/java/FileBasedTests.java
index 4edb8fa12..64ce64493 100644
--- a/palantir-java-format/src/test/java/com/palantir/javaformat/java/FileBasedTests.java
+++ b/palantir-java-format/src/test/java/com/palantir/javaformat/java/FileBasedTests.java
@@ -59,7 +59,8 @@ public final class FileBasedTests {
                             "SwitchUnderscore",
                             "I880",
                             "I1309",
-                            "Unnamed")
+                            "Unnamed",
+                            "UnnamedPattern")
                     .build();
 
     private final Class<?> testClass;
diff --git a/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.input b/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.input
new file mode 100644
index 000000000..9eb7739a2
--- /dev/null
+++ b/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.input
@@ -0,0 +1,19 @@
+class UnnamedPattern {
+    public static void main(String[] args) {
+        var cp = new ColoredPoint(new Point(1, 2), Color.RED);
+
+        // The colour doesn't matter, so use an unnamed pattern
+        // (as opposed to the unnamed type pattern `var _`).
+        if (cp instanceof ColoredPoint(Point(int x, int y), _)) {
+            System.out.println(x + "," + y);
+        }
+
+        if (cp instanceof ColoredPoint(_, var c)) {
+            System.out.println(c);
+        }
+    }
+}
+
+record Point(int x, int y) { }
+enum Color { RED, GREEN, BLUE }
+record ColoredPoint(Point p, Color c) { }
diff --git a/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.output b/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.output
new file mode 100644
index 000000000..656d40d4f
--- /dev/null
+++ b/palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/UnnamedPattern.output
@@ -0,0 +1,25 @@
+class UnnamedPattern {
+    public static void main(String[] args) {
+        var cp = new ColoredPoint(new Point(1, 2), Color.RED);
+
+        // The colour doesn't matter, so use an unnamed pattern
+        // (as opposed to the unnamed type pattern `var _`).
+        if (cp instanceof ColoredPoint(Point(int x, int y), _)) {
+            System.out.println(x + "," + y);
+        }
+
+        if (cp instanceof ColoredPoint(_, var c)) {
+            System.out.println(c);
+        }
+    }
+}
+
+record Point(int x, int y) {}
+
+enum Color {
+    RED,
+    GREEN,
+    BLUE
+}
+
+record ColoredPoint(Point p, Color c) {}