In Grand Theft Auto V, what was Michael De Santa's former surname?

In Grand Theft Auto V, Michael De Santa's former surname is Townley. Michael changed his surname as part of his identity change after he entered witness protection. This was necessary because Michael De Santa is actually a former bank robber who faked his death and turned informant for the FIB. Changing his surname was a crucial step in creating a new life for himself and his family while staying off the radar of his former criminal associates.