The 57-year-old Spaniard replaces David Moyes, who left when his contract expired at the end of the season.
Lopetegui has previously been in charge at Porto, Spain, Real Madrid and Sevilla prior to a brief stint with Wolves.
Julen Lopetegui has vowed to make a “big, big noise” at West Ham United after his appointment as the successor to David Moyes was confirmed on Thursday.