A breakaway coupling includes a body and a valve assembly inside the body. The body includes a fluid conduit and a shear groove between first and second portions. The shear groove is designed to crack, break, or separate under certain conditions. The valve assembly is designed to shut off fluid flow through the fluid conduit when the shear groove cracks, breaks, or separates. The valve assembly includes a valve seat, a sealing element, one or more pins, and a biasing member. The one or more pins hold the sealing element in an open position while the shear groove is in tack, and allow the sealing element to move to a closed position (with the help of the biasing member) in the event the shear groove cracks, breaks, or separates.