Systems and methods for controlling flow with a 270 degree rotatable valve are provided. A described system includes a valve body having a valve chamber and a plurality of ports into the valve chamber. The plurality of ports include a first port, a second port, and a third port. The first port and the second port are aligned with a common axis and located on opposite sides of the valve chamber. The system further includes a valve member located within the valve chamber. The valve member is controllably rotatable by approximately 270 degrees to modulate fluid flow between the first port and the third port while maintaining the second port completely closed and to modulate fluid flow between the second port and the third port while maintaining the first port completely closed.