Serialization and deserialization in Java are essential processes for converting objects into a byte-stream representation and vice versa. Serialization allows Java objects to be transformed into a sequence of bytes, which can be stored in files or transmitted over networks. This is particularly useful for persisting object states beyond the lifecycle of a Java Virtual Machine (JVM). Deserialization, on the other hand, is the process of reconstructing the original object from the byte-stream. Both processes are facilitated by the java.io.Serializable interface, which marks classes as serializable, ensuring compatibility during the serialization and deserialization processes.