diff --git a/src/Model/BSONIterator.php b/src/Model/BSONIterator.php
new file mode 100644
index 000000000..d54c123a6
--- /dev/null
+++ b/src/Model/BSONIterator.php
@@ -0,0 +1,135 @@
+<?php
+/*
+ * Copyright 2018 MongoDB, Inc.
+ *
+ * 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
+ *
+ *   http://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.
+ */
+
+namespace MongoDB\Model;
+
+use MongoDB\Exception\UnexpectedValueException;
+use MongoDB\Model\BSONDocument;
+use Iterator;
+
+/**
+ * Iterator for BSON documents.
+ */
+class BSONIterator implements Iterator
+{
+    private $buffer;
+    private $bufferLength;
+    private $current;
+    private $key = 0;
+    private $position = 0;
+    private $options;
+
+    const BSON_SIZE = 4;
+
+    /**
+     * Constructs a BSON Iterator.
+     *
+     * Supported options:
+     *
+     *  * typeMap (array): Type map for BSON deserialization.
+     *
+     * @internal
+     * @see http://php.net/manual/en/function.mongodb.bson-tophp.php
+     * @param string $data    Concatenated, valid, BSON-encoded documents
+     * @param array  $options Iterator options
+     * @throws InvalidArgumentException for parameter/option parsing errors
+     */
+    public function __construct($data, array $options = [])
+    {
+        if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
+            throw InvalidArgumentException::invalidType('"typeMap" option', $options['typeMap'], 'array');
+        }
+
+        if ( ! isset($options['typeMap'])) {
+            $options['typeMap'] = [];
+        }
+
+        $this->buffer = $data;
+        $this->bufferLength = strlen($data);
+        $this->options = $options;
+    }
+
+    /**
+     * @see http://php.net/iterator.current
+     * @return mixed
+     */
+    public function current()
+    {
+        return $this->current;
+    }
+
+    /**
+     * @see http://php.net/iterator.key
+     * @return mixed
+     */
+    public function key()
+    {
+        return $this->key;
+    }
+
+    /**
+     * @see http://php.net/iterator.next
+     * @return void
+     */
+    public function next()
+    {
+        $this->key++;
+        $this->current = null;
+        $this->advance();
+    }
+
+    /**
+     * @see http://php.net/iterator.rewind
+     * @return void
+     */
+    public function rewind()
+    {
+        $this->key = 0;
+        $this->position = 0;
+        $this->current = null;
+        $this->advance();
+    }
+
+    /**
+     * @see http://php.net/iterator.valid
+     * @return boolean
+     */
+    public function valid()
+    {
+        return $this->current !== null;
+    }
+
+    private function advance()
+    {
+        if ($this->position === $this->bufferLength) {
+            return;
+        }
+
+        if (($this->bufferLength - $this->position) < self::BSON_SIZE) {
+            throw new UnexpectedValueException(sprintf('Expected at least %d bytes; %d remaining', self::BSON_SIZE, $this->bufferLength - $this->position));
+        }
+
+        list(,$documentLength) = unpack('V', substr($this->buffer, $this->position, self::BSON_SIZE));
+
+        if (($this->bufferLength - $this->position) < $documentLength) {
+            throw new UnexpectedValueException(sprintf('Expected %d bytes; %d remaining', $documentLength, $this->bufferLength - $this->position));
+        }
+
+        $this->current = \MongoDB\BSON\toPHP(substr($this->buffer, $this->position, $documentLength), $this->options['typeMap']);
+        $this->position += $documentLength;
+    }
+}
diff --git a/tests/Model/BSONIteratorTest.php b/tests/Model/BSONIteratorTest.php
new file mode 100644
index 000000000..182f461cd
--- /dev/null
+++ b/tests/Model/BSONIteratorTest.php
@@ -0,0 +1,133 @@
+<?php
+
+namespace MongoDB\Tests\Model;
+
+use MongoDB\Exception\UnexpectedValueException;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
+use MongoDB\Model\BSONIterator;
+use MongoDB\Tests\TestCase;
+use stdClass;
+
+class BSONIteratorTest extends TestCase
+{
+    /**
+     * @dataProvider provideTypeMapOptionsAndExpectedDocuments
+     */
+    public function testValidValues(array $typeMap = null, $binaryString, array $expectedDocuments)
+    {
+        $bsonIt = new BSONIterator($binaryString, ['typeMap' => $typeMap]);
+
+        $results = iterator_to_array($bsonIt);
+
+        $this->assertEquals($expectedDocuments, $results);
+    }
+
+    public function provideTypeMapOptionsAndExpectedDocuments()
+    {
+        return [
+            [
+                null,
+                implode(array_map(
+                    'MongoDB\BSON\fromPHP',
+                    [
+                        ['_id' => 1, 'x' => ['foo' => 'bar']],
+                        ['_id' => 3, 'x' => ['foo' => 'bar']],
+                    ]
+                )),
+                [
+                    (object) ['_id' => 1, 'x' => (object) ['foo' => 'bar']],
+                    (object) ['_id' => 3, 'x' => (object) ['foo' => 'bar']],
+                ]
+            ],
+            [
+                ['root' => 'array', 'document' => 'array'],
+                implode(array_map(
+                    'MongoDB\BSON\fromPHP',
+                    [
+                        ['_id' => 1, 'x' => ['foo' => 'bar']],
+                        ['_id' => 3, 'x' => ['foo' => 'bar']],
+                    ]
+                )),
+                [
+                    ['_id' => 1, 'x' => ['foo' => 'bar']],
+                    ['_id' => 3, 'x' => ['foo' => 'bar']],
+                ]
+            ],
+            [
+                ['root' => 'object', 'document' => 'array'],
+                implode(array_map(
+                    'MongoDB\BSON\fromPHP',
+                    [
+                        ['_id' => 1, 'x' => ['foo' => 'bar']],
+                        ['_id' => 3, 'x' => ['foo' => 'bar']],
+                    ]
+                )),
+                [
+                    (object) ['_id' => 1, 'x' => ['foo' => 'bar']],
+                    (object) ['_id' => 3, 'x' => ['foo' => 'bar']],
+                ]
+            ],
+            [
+                ['root' => 'array', 'document' => 'stdClass'],
+                implode(array_map(
+                    'MongoDB\BSON\fromPHP',
+                    [
+                        ['_id' => 1, 'x' => ['foo' => 'bar']],
+                        ['_id' => 3, 'x' => ['foo' => 'bar']],
+                    ]
+                )),
+                [
+                    ['_id' => 1, 'x' => (object) ['foo' => 'bar']],
+                    ['_id' => 3, 'x' => (object) ['foo' => 'bar']],
+                ]
+            ],
+        ];
+    }
+
+    public function testCannotReadLengthFromFirstDocument()
+    {
+        $binaryString = substr(\MongoDB\BSON\fromPHP([]), 0, 3);
+
+        $bsonIt = new BSONIterator($binaryString);
+
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('Expected at least 4 bytes; 3 remaining');
+        $bsonIt->rewind();
+    }
+
+    public function testCannotReadLengthFromSubsequentDocument()
+    {
+        $binaryString = \MongoDB\BSON\fromPHP([]) . substr(\MongoDB\BSON\fromPHP([]), 0, 3);
+
+        $bsonIt = new BSONIterator($binaryString);
+        $bsonIt->rewind();
+
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('Expected at least 4 bytes; 3 remaining');
+        $bsonIt->next();
+    }
+
+    public function testCannotReadFirstDocument()
+    {
+        $binaryString = substr(\MongoDB\BSON\fromPHP([]), 0, 4);
+
+        $bsonIt = new BSONIterator($binaryString);
+
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('Expected 5 bytes; 4 remaining');
+        $bsonIt->rewind();
+    }
+
+    public function testCannotReadSecondDocument()
+    {
+        $binaryString = \MongoDB\BSON\fromPHP([]) . substr(\MongoDB\BSON\fromPHP([]), 0, 4);
+
+        $bsonIt = new BSONIterator($binaryString);
+        $bsonIt->rewind();
+
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('Expected 5 bytes; 4 remaining');
+        $bsonIt->next();
+    }
+}