A hammer union back pressure regulator is provided. The hammer union back pressure regulator comprises a regulator body, a bonnet, a housing and a flow control member. The regulator body defines a flow inlet, a flow outlet, and a flow passage in fluid communication with the flow inlet and the flow outlet. The bonnet is coupled to the regulator body with a hammer union nut. The flow control member is configured to adjust the pressure at which the hammer union back pressure regulator will allow flow through the flow passage.