The School of Infantry (SOI) at United States Marine Corps base Camp Lejeune and the School of Infantry (West) at Camp Pendleton, host the second stage of initial military training for enlisted Marines after boot camp.

The school contains both the Infantry Training Battalion (ITB) where Marines in the infantry Military Occupational Specialty (MOS) are trained, and the Marine Combat Training (MCT) Battalion, where all other enlisted Marines receive training in basic infantry weapons and tactics.

Prior to 1997, only male Marines were trained at SOI schools, females went directly to their MOS schools. In 1997 the school at Camp Lejeune expanded its program to include all new female enlistees. SOI (West) continues to train only males, similar to the west coast recruit depot at MCRD San Diego.