A combat engineer (also called pioneer or sapper) is a type of soldier who performs military engineering tasks in support of land forces combat operations. Combat engineers perform a variety of military engineering, tunnel and mine warfare tasks as well as construction and demolition duties in and out of combat zones.

Combat engineers facilitate the mobility of friendly forces while impeding that of the enemy. They also work to assure the survivability of friendly forces, building fighting positions, fortifications, and roads. They conduct demolition missions and clear minefields manually or through use of specialized vehicles. Common combat engineer missions include construction and breaching of trenches, tank traps and other obstacles and fortifications; obstacle emplacement and bunker construction; route clearance and reconnaissance; bridge and road construction or destruction; emplacement and clearance of land mines; and combined arms breaching. Typically, combat engineers are also trained in infantry tactics and, when required, serve as provisional infantry.