The Mobile Infantry (MI) is a fictional military force in the novel Starship Troopers and the 1997 film of the same name. The MI is portrayed differently in both versions.

The Mobile Infantry of The Terran Federation (Novel)

The Mobile Infantry is an Elite Fighting force similar to the United States Marine Corps. It is unknown whether the MI is indeed a separate branch of the Terran Federation Military or a Special Ops Unit within the Army. A Mobile Infantryman is equipped with a Powered Suit as well as an arsenal of weapons at his disposal, some built in to the suit. These weapons range from conventional firearms to micro-nuclear warheads.

Usually, an MI platoon would drop from individual capsules launched from a troop transport. The Capsule is used only once. The MI Platoon will then execute its mission. These missions range from Hit-and-Run Strikes to Search and Rescue missions. After the mission is complete, the Transport will launch an Audio Beacon for the Platoon to follow to the retrieval area. Usually the Beacon will play music such as, in the case of the TFCT Rodger Young, The Ballad of Rodger Young. Once the Dropship lands, the Platoon boards and returns to the Transport.

The MI prides itself in its Esprit de Corps. This philosophy includes never leaving a wounded soldier for dead; instead they pick up their wounded and make sure they make it back alive.

The Mobile Infantry of the United Citizen Federation (1997 Movie)

The Mobile Infantry in the Movie is vastly different from its novel counterpart. Instead of an Elite Fighting Force equipped with Powered Suits, they are a conventional army armed with conventional weapons.

The MI troops were also portrayed as more expendable than in the book. When Johnnie and Carmen enlist, the desk sergeant refers to them as "fresh meat for the grinder".