A wonderful injury-time winner from midfielder John Rankin handed Inverness their second sensational win over Rangers this season and left the Ibrox club in third place in the Bank of Scotland Premier League following a 2-1 loss.
A disappointing Rangers side opened the scoring from the penalty spot midway through the first half through Nacho Novo, after Roy McBain needlessly fouled Barry Ferguson.
But Darren Dods equalised just before the break, before Rankin's brilliant winner ended a nine-match winless run for Charlie Christie's team and added to Caley Thistle's 1-0 win at Ibrox in October.
It was Inverness who took the game to Rangers in the early stages and inside five minutes the home side fashioned three good chances, the first of which fell to Graham Bayne, who drove a low shot towards Allan McGregor in the Rangers' goal, which was comfortably saved.
Jeremy Clement was then forced to hack a Bayne header away from his goalline before Rankin wasted a good opportunity when he sliced a half-volley well off target after good play by Dennis Wyness.
Rangers finally started to become an attacking threat in the 11th minute and a neat pass from Clement sent Filip Sebo scampering through on goal, although brave goalkeeping from Mark Brown snuffed out any danger.
Shortly afterwards, Libor Sionko headed over from a cross by Sasa Papac, while Charlie Adam tested Brown with a 25-yard drive following a driving run by Ferguson and a clever lay-off by Novo.
The breakthrough for Rangers then came in the 22nd minute from the penalty spot, when after McBain clipped an ankle of Ferguson inside the Caley Thistle box, Novo confidently beat Brown from 12 yards.
Inverness responded to that setback in positive fashion and a surge down the right by defender Ross Tokely followed by a cut-back to Rankin saw the Caley Thistle midfielder draw a strong block from McGregor down to the goalkeeper's left-hand side.
Any zest the visitors had previously displayed was now absent from their play and after forging a number of openings against a fragile looking Rangers' rearguard, it was no real surprise when Inverness scored an equaliser.
A mis-hit pass from Grant Munro sent Dods through on goal and after drawing a great save from McGregor with his first effort, the Caley Thistle captain lashed the ball into an unguarded goal via the crossbar.
Rangers' keeper McGregor did well to intelligently clear away a volleyed back-pass from Alan Hutton with his head seven minutes after the restart as a through-ball from Wyness looked set to carve open the Ibrox club's defence.
Rankin subsequently fired wide from the edge of the box before the former Ross County midfielder struck the foot of a post from an acute angle after a shot from Wilson broke into his path.
McGregor was soon forced another brilliant save, this time from a curling Black shot, while a powerful Wyness shot from the edge of the box had to be beaten away.
But the visiting goalkeeper could do nothing to prevent Rankin's outstanding last-gasp strike, which means Rangers remain two points behind second-placed Aberdeen in the Bank of Scotland Premier League.
