Ross County beat Inverness CT for the first time since 2009, which helped edge their Highland rivals out of a Europa League spot for season 2013/14.
Canadian defender Andre Hainault put the hosts in front with a fine 10-yard volley just before half-time.
Billy McKay's opportunistic flick from David Raven's shot almost pegged back County, who had Iain Vigurs hit the post from a free-kick near the end.
St Johnstone leapfrogged Caley Thistle into third by beating Motherwell .
Despite having held second or third place in the Scottish Premier League for much of the season, Caley Thistle's loss in Dingwall means that they finish fourth, two points behind the Perth side.
No maiden journey into European football now awaits Terry Butcher's men.
Fifth-placed County have only lost two of their last 15 matches at Victoria Park and they will be delighted to get their first Highland derby win in eight attempts.
A calf injury to Michael Fraser meant goalkeeper Paul Gallacher made his Ross County debut and he comfortably dealt with Charlie Taylor's bobbling shot from distance in the opening exchanges.
But some would argue the former Dunfermline stopper should have been picking the ball out of the net when Caley Thistle defender Danny Devine stretched to turn Aaron Doran's corner wide of the post from six yards.
At the other end, Sproule, so often clinical for the hosts this season, side-footed over the crossbar from eight yards after Evangelos Ikonomou's low centre from the left-hand side.
County's Mihael Kovacevic took matters into his own hands as he darted from deep to toe-poke a 20-yard effort into the arms of visiting goalkeeper Antonio Reguero.
And, minutes later, the hosts' German striker, Steffen Wohlfarth, had Kilmarnock-bound Reguero scrambling across his goal-mouth with a speculative volley that skidded wide.
Butcher altered his midfield by replacing Conor Pepper with Nick Ross, but County's attacking continued as midfielder Stuart Kettlewell's 25-yard strike curled inches wide.
And, with half-time approaching, Derek Adams' side got the breakthrough from an unlikely source.
It was centre-back Hainault whose terrific volley lashed into the back of the net after a headed clearance from Paul Lawson's cross had fallen to the Canadian.
After the break, Caley Thistle's Aaron Doran tested Gallacher from distance, but County's impressive forward play resumed.
Sproule's dangerous cross from the right was followed by another from the left by Ikonomou that Wohlfarth nearly turned into the goal.
However, the visitors' equaliser almost arrived in strange fashion when striker McKay stuck a leg out to divert Raven's long-range strike narrowly past the upright.
End-to-end football ensued as Doran shot high for Inverness before County's Lawson had two efforts well blocked by the Inverness rear-guard.
Marauding running down the left by Ikonomou troubled Inverness all afternoon and it won the hosts a free-kick from which Vigurs hit the post.
Reguero also denied Vigurs at the death to prevent County doubling their lead.
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