diff --git a/src/Validators/Dictionary.php b/src/Validators/Dictionary.php
new file mode 100644
index 0000000..4ba0dd9
--- /dev/null
+++ b/src/Validators/Dictionary.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Firehed\Input\Validators;
+
+use stdClass;
+
+use function is_array;
+
+class Dictionary implements ValidatorInterface
+{
+    /**
+     * @param ValidatorInterface[] $required
+     * @param ValidatorInterface[] $optional
+     */
+    public function __construct(
+        private array $required,
+        private array $optional = [],
+        private bool $rejectUnexpected = true,
+    ) {
+    }
+
+    public function validate(mixed $decoded): Result
+    {
+        return match (true) {
+            is_array($decoded) => $this->validateArray($decoded),
+            $decoded instanceof stdClass => $this->validateObject($decoded),
+        };
+    }
+
+    private function validateArray(array $decoded)
+    {
+        foreach ($decoded as $key => $value) {
+            // if in required, force validation
+            // if in optional, still force validation
+            // if in neither, examine $rejectUnexpected
+        }
+        // check if any optional values are not yet in the output & apply their
+        // default values
+    }
+
+    private function validateObject(stdClass $decoded)
+    {
+    }
+
+    public function getDefaultValue()
+    {
+    }
+}
diff --git a/src/Validators/ListOf.php b/src/Validators/ListOf.php
new file mode 100644
index 0000000..056bcf4
--- /dev/null
+++ b/src/Validators/ListOf.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Firehed\Input\Validators;
+
+use function is_iterable;
+
+/**
+ * @implements ValidatorInterface<Item[]>
+ * @template Item
+ */
+class ListOf implements ValidatorInterface
+{
+    /**
+     * @param ValidatorInterface<Item> $validator
+     */
+    public function __construct(private ValidatorInterface $validator)
+    {
+    }
+
+    public function validate(mixed $decoded): Result
+    {
+        if (!is_iterable($decoded)) {
+            return Result::error('Value is not convertable to a list');
+        }
+        // Normally array_map would be preferred here, but this avoids having
+        // to do any additional type juggling (for non-array iterables) or
+        // re-keying (for ensuring array_is_list(result))
+        $output = [];
+        foreach ($decoded as $item) {
+            $output[] = $this->validator->validate($item);
+        }
+        return Result::ok(
+            array_map(fn ($item) => $item->unwrap(), $output)
+        );
+    }
+}
diff --git a/src/Validators/Nullable.php b/src/Validators/Nullable.php
new file mode 100644
index 0000000..e9f8f8f
--- /dev/null
+++ b/src/Validators/Nullable.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Firehed\Input\Validators;
+
+/**
+ * @template NonNullable
+ * @implements ValidatorInterface<NonNullable | null>
+ */
+class Nullable implements ValidatorInterface
+{
+    /**
+     * @param ValidatorInterface<NonNullable> $validator
+     */
+    public function __construct(private ValidatorInterface $validator)
+    {
+    }
+
+    public function validate(mixed $decoded): Result
+    {
+        if ($decoded === null) {
+            return Result::ok(null);
+        }
+        return $this->validator->validate($decoded);
+    }
+}