Match ends, Ross County 2, Dundee United 3.
Billy Mckay's late goal put Dundee United into the Scottish Cup semi-final after a five-goal thriller in Dingwall.
Liam Boyce headed Ross County into the lead from close range, with Henri Anier levelling after the break.
United defender Mark Durnan was sent off for a last-man foul on Brian Graham, who buried the resulting penalty to put County back in front.
Anier equalised again before Mckay's header from Blair Spittal's cross sealed a memorable cup win.
Boyce and Graham came into the County side while Anier was included in the United line-up, a decision that had a big bearing on the outcome.
It was Boyce who set County on their way with a close-range header from a well-worked set piece as Jim McIntyre looked good to add a Scottish Cup semi-final to next week's League Cup final appearance.
United were limited to long-range efforts in the opening period, all of which were way off target as both sides showed tremendous will to get forward but perhaps lacked composure in front of goal on a tricky surface.
United started the second half brightly when Anier seized on Durnan's deflected shot and fired past Woods to equalise.
It went horribly wrong for Mixu Paatelainen's side almost instantly when Durnan was ordered off for a challenge on Graham in the box. Referee Craig Thomson awarded the penalty and Graham simply slammed the ball low into the net.
All indicators suggested United's chance was gone but they went on to produce an outstanding, committed performance.
It developed into a classic Scottish Cup tie and incredibly Anier equalised for a second time when he anticipated the flight of the ball and arrived at the back post to slot home and send the large travelling support wild.
Both sides continued to go forward with Spittal and Michael Gardyne going close but in the last minute of the 90, United sealed a famous win.
Spittal delivered accurately from the right-hand side and for the second week running Mckay netted from close range, this time with a header to send United through.
What this does for Dundee United's season remains unclear but they proved something when everything was against them.
Their priority might be staying in the Premiership but this win and performance might prove valuable on all fronts.
- 17FranksSubstituted forDe Vitaat 76'minutes
- 26WoodsSubstituted forMcShaneat 61'minutes
- 9GrahamSubstituted forSchalkat 68'minutes
- 24De Vita
- 17DurnanBooked at 59mins
- 6PatonSubstituted forKnoyleat 66'minutes
- 8RankinBooked at 75mins
- 26AnierBooked at 57minsSubstituted forErskineat 83'minutes
- Craig Thomson
- Shots on Target
Second Half ends, Ross County 2, Dundee United 3.
Attempt missed. Liam Boyce (Ross County) right footed shot from the centre of the box is close, but misses to the right.
Goal! Ross County 2, Dundee United 3. Billy McKay (Dundee United) header from very close range to the centre of the goal. Assisted by Blair Spittal.
Richard Foster (Ross County) wins a free kick on the right wing.
Foul by Billy McKay (Dundee United).
Attempt missed. Raffaele De Vita (Ross County) header from the left side of the six yard box is just a bit too high.
Attempt missed. Ian McShane (Ross County) right footed shot from outside the box is close, but misses to the left.
Corner, Ross County. Conceded by Coll Donaldson.
Substitution, Dundee United. Chris Erskine replaces Henri Anier.
Attempt missed. John Rankin (Dundee United) right footed shot from outside the box is high and wide to the left.
Corner, Dundee United. Conceded by Ian McShane.
Corner, Ross County. Conceded by Luis Maria Zwick.
Attempt saved. Michael Gardyne (Ross County) left footed shot from the right side of the box is saved in the bottom left corner.
Attempt saved. Blair Spittal (Dundee United) right footed shot from the right side of the box is saved in the bottom right corner.
Foul by Raffaele De Vita (Ross County).
Blair Spittal (Dundee United) wins a free kick in the defensive half.
Substitution, Ross County. Raffaele De Vita replaces Jonathan Franks.
Attempt saved. Paul Quinn (Ross County) right footed shot from outside the box is saved in the centre of the goal.
John Rankin (Dundee United) is shown the yellow card for a bad foul.