The Bell Aerosystems Company XLR81 (Model 8096) was an American liquid-propellant rocket engine, which was used on the Agena upper stage.

It burned UDMH and RFNA fed by a turbopump in a fuel rich gas generator cycle.

The turbopump had a single turbine with a gearbox to transmit power to the oxidizer and fuel pumps.

The engine was mounted on a hydraulic actuated gimbal which enabled thrust vectoring to control pitch and yaw.

[5] Starting as an air-launched missile engine and finishing as a multi-mission general propulsion for the space age, the basic design went through a series of iterations and versions that enabled it to have a long and productive career.