Steen Erik Mastrup (born 2 June 1958) is a Danish former motorcycle speedway rider.Born in Naestved, Mastrup established himself in Danish speedway and represented Denmark at under-21 level in 1977. He made his British League debut in 1978 with Swindon Robins. By 1981 his average had risen to above six points per match. He was capped several times in the full Denmark team. After an injury in 1982 he suffered a drop in form in 1983 and transferred to Leicester Lions.