diff --git a/library/error/api/error.api b/library/error/api/error.api
index e69de29..3001060 100644
--- a/library/error/api/error.api
+++ b/library/error/api/error.api
@@ -0,0 +1,5 @@
+public final class org/kotlincrypto/error/PreconditionsKt {
+	public static final fun requireParam (Z)V
+	public static final fun requireParam (ZLkotlin/jvm/functions/Function0;)V
+}
+
diff --git a/library/error/api/error.klib.api b/library/error/api/error.klib.api
index 4d60cc2..6376a3b 100644
--- a/library/error/api/error.klib.api
+++ b/library/error/api/error.klib.api
@@ -67,3 +67,6 @@ open class org.kotlincrypto.error/ShortBufferException : org.kotlincrypto.error/
     constructor <init>() // org.kotlincrypto.error/ShortBufferException.<init>|<init>(){}[0]
     constructor <init>(kotlin/String?) // org.kotlincrypto.error/ShortBufferException.<init>|<init>(kotlin.String?){}[0]
 }
+
+final inline fun org.kotlincrypto.error/requireParam(kotlin/Boolean) // org.kotlincrypto.error/requireParam|requireParam(kotlin.Boolean){}[0]
+final inline fun org.kotlincrypto.error/requireParam(kotlin/Boolean, kotlin/Function0<kotlin/Any>) // org.kotlincrypto.error/requireParam|requireParam(kotlin.Boolean;kotlin.Function0<kotlin.Any>){}[0]
diff --git a/library/error/src/commonMain/kotlin/org/kotlincrypto/error/Preconditions.kt b/library/error/src/commonMain/kotlin/org/kotlincrypto/error/Preconditions.kt
new file mode 100644
index 0000000..1c29255
--- /dev/null
+++ b/library/error/src/commonMain/kotlin/org/kotlincrypto/error/Preconditions.kt
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Matthew Nelson
+ *
+ * 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
+ *
+ *     https://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.
+ **/
+@file:Suppress("KotlinRedundantDiagnosticSuppress", "NOTHING_TO_INLINE")
+
+package org.kotlincrypto.error
+
+import kotlin.contracts.ExperimentalContracts
+import kotlin.contracts.contract
+
+/**
+ * Throws [InvalidParameterException] when [condition] is false.
+ * */
+@OptIn(ExperimentalContracts::class)
+public inline fun requireParam(condition: Boolean) {
+    contract {
+        returns() implies condition
+    }
+    requireParam(condition) { "Parameter check failed." }
+}
+
+/**
+ * Throws [InvalidParameterException] with the result of calling [lazyMessage] when [condition] is false.
+ * */
+@OptIn(ExperimentalContracts::class)
+public inline fun requireParam(condition: Boolean, lazyMessage: () -> Any) {
+    contract {
+        returns() implies condition
+    }
+    if (condition) return
+    val message = lazyMessage()
+    throw InvalidParameterException(message.toString())
+}
diff --git a/library/error/src/commonTest/kotlin/org/kotlincrypto/error/PreconditionsUnitTest.kt b/library/error/src/commonTest/kotlin/org/kotlincrypto/error/PreconditionsUnitTest.kt
new file mode 100644
index 0000000..6dde126
--- /dev/null
+++ b/library/error/src/commonTest/kotlin/org/kotlincrypto/error/PreconditionsUnitTest.kt
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2025 Matthew Nelson
+ *
+ * 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
+ *
+ *     https://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 org.kotlincrypto.error
+
+import kotlin.test.Test
+import kotlin.test.assertFailsWith
+
+class PreconditionsUnitTest {
+
+    @Test
+    fun givenRequireParam_whenConditionTrue_thenDoesNotThrow() {
+        requireParam(true)
+        requireParam(true) { "fail" }
+    }
+
+    @Test
+    fun givenRequireParam_whenConditionFalse_thenThrows() {
+        assertFailsWith<InvalidParameterException> { requireParam(false) }
+        assertFailsWith<InvalidParameterException> { requireParam(false) { "fail" } }
+    }
+}