Lamont signed a two-year deal and will join the Saints at the end of the season from Glasgow.
Lamont, 24, scored for Glasgow against Northampton in the European Cup earlier this year and is a physical, hard-running winger that Saints head coach Budge Pountney is delighted to have on board.
"He has shown us already this year what a raw talent he is in the European Cup when he tore teams apart, including us, with his incisive runs," said Pountney.
"He is in the mould of a big, physical winger with pace and a high work-rate but also proves to be very elusive on the rugby pitch.
"We are very much looking forward to working with him here at the Saints."