Fluid circulation valve is provided for use with a well drilling operation, so that a drill joint may be added to or removed from the drill string while continuously circulating fluid into the well. Valve housing has a central flow path therein, a housing side port, and upper and lower threaded connectors for engagement with the drill joint and the drill string, respectively. A rotatable ball is positioned within the flow path in the valve housing and a port in the ball is in fluid communication with the housing side port when the ball is closed. A coupling is provided for engaging the valve housing and sealing between an interior of the valve housing and the radially external flow line, which passes fluid into the well when a drill joint is being connecting to the upper end of the valve.