Deserialization in Symfony is the reverse process of serialization: it allows converting data in JSON, XML, or other formats into PHP objects. This mechanism is particularly useful for transforming data received from an API or a file into manipulatable objects within an application. Symfony uses its Serializer component to perform this conversion while supporting complex data structures and specific rules. You can map the deserialized data to the properties of a class while applying validation constraints. Therefore, deserialization is essential for effectively receiving and processing data in Symfony applications, ensuring its integrity and compliance with system requirements.