The present disclosure includes apparatuses and methods related to memory module interfaces. A memory module, which may include volatile memory or nonvolatile memory, or both, may be configured to communicate with a host device via one interface and to communicate with another memory module using a different interface. Memory modules may thus be added or removed from a system without impacting a PCB-based bus to the host, and memory modules may communicate with one another without accessing a bus to the host. The host interface may be configured according to one protocol or standard, and other interfaces between memory modules may be configured according to other protocols or standards.