A Stevie May double helped St Johnstone come from behind to beat Aberdeen 2-1 to set pu a date with Dundee United in their first ever appearance in a Scottish Cup final on Sunday

The Dons had taken a 16th minute lead through Niall McGinn who applied a cool finish to a free-flowing move that cut right through the St Johnstone defence.

However, Saints came out flying in the second half and grabbed a deserved equaliser through Scotland under-21 striker May in the 61st minute.

May was denied a second by Langfield before Barry Robson and Niall McGinn missed good headed opportunities for Aberdeen.

With time running out May scored a superb solo second in the 84th minute as Saints gained revenge for their League Cup semi-final defeat to the Dons.

It is ninth time lucky for the Saints, who had previously appeared in eight cup semi-finals without ever making a final, and ends the Dons hopes of making it a cup double this season after claiming the League Cup in March.

They now face Dundee United who beat Rangers 3-1 on Saturday.

Aberdeen had demolished St Johnstone 4-0 in their League Cup semi-final meeting in February and started brightly at Ibrox with Robson flashing a shot just wide after his free-kick rebounded back to him off the St Johnstone wall.

The Dons faithful didn't have to wait long to celebrate though as they cut through the St Johnstone defence for a 16th minute opener.

Adam Rooney laid the ball off to Peter Pawlett who fed McGinn and the Northern Irishman kept his cool to roll the ball under Alan Mannus.

St Johnstone were quick out of the traps after the break and Frazer Wright was first to test Langfield with a headed flick-on that May came close to connecting with.

Aberdeen had a chance to increase their lead in the 57th minute when McGinn broke down the left wing before cutting the ball back to Pawlett at the edge of the box but he wildly sliced his shot out for a throw-in.

The Dons were left to rue that missed opportunity four minutes later when May fired St Johnstone level. David Wootherspoon's corner was knocked back into the box by James Dunne and, with his back to goal, May took a touch before swivelling and rifling a shot under the legs of the despairing Langfield.

May almost had a second a minute later when Langfield had to be at full stretch to tip away his curling effort.

The momentum switched to Aberdeen and the Dons should have been ahead in the 68th minute when the unchallenged Robson sent a header straight at Mannus from six yards out.

Robson then turned provider as he picked out the unmarked McGinn at the back post with his cross from the right but the striker put his header wide of the target.

May sent the Saints fans wild with an 83rd minute winner. He headed the ball to Steven MacLean before collecting the return and drilling a fierce strike beyond Langfield from just inside the box.