Charith Asalanka's maiden one-day international century and an inspired spin attack led Sri Lanka to a thrilling four-run series-clinching win over Australia on Tuesday.
The left-handed Asalanka made 110 to guide Sri Lanka to 258 all out, a total that proved just enough to hand the hosts an unbeatable 3-1 lead in the five-match series in Colombo.
Opener David Warner's 99 went in vain as Australia were bowled out for 254 and the island nation won its first bi-lateral series against the Aussies in over a decade. They last won in 2010.
Spinners Dhananjaya de Silva, Jeffrey Vandersay and fast bowler Chamika Karunaratne, who was the only regular seamer in the team, took two wickets each.
Pat Cummins' late cameo of 35 and a 12-ball 15 by number 10 Matthew Kuhnemann, who hit three fours as Australia needed 19 from the 50th over, gave Sri Lanka a scare.
Earlier Asalanka rescued Sri Lanka from a precarious 34-3 as he put on 101 runs with Dhananjaya de Silva, who made 60.
Australian bowlers kept coming back with crucial wickets but Asalanka reached his century to the cheers of a raucous home crowd that jumped to their feet to applaud the knock.
Wanindu Hasaranga played a useful cameo of 21 not out as he put together 34 runs for the eighth wicket with Asalanka.
Asalanka finally fell to Cummins and Australia soon wrapped up the innings in 49 overs with two run outs.
In reply, Australia lost skipper Aaron Finch for nought with Karunaratne trapping the opener lbw.
Warner kept his cool and put on 63 runs with Mitchell Marsh who looked good for his 26 before he fell to Dunith Wellalage's left-arm spin.
Australia lost Marnus Labuschagne and wicketkeeper-batsman Alex Carey after they got starts but fell to the Sri Lankan spinners.
The usually attacking Warner held fort to try and grind down the opposition attack as he got Travis Head for company and the two stitched together 58 runs for the fifth wicket.
De Silva bowled the left-handed Head for 27 and Maheesh Theekshana got Glenn Maxwell trapped lbw for one with a successful review after the on-field umpire denied the appeal.
But the big moment came when the left-handed Warner missed out on his ton after getting stumped off de Silva as the home team celebrated the key wicket.
Cameron Green and Cummins attempted to turn the chase on in a 31-run stand but Vandersay bowled Green.
Cummins departed in the 49th over but Kuhnemann fought till the end before getting out on the final ball.
The final match is on Friday at the same venue.
Sri Lanka v Australia fourth ODI scoreboard
Final scoreboard of the fourth one-day international between Sri Lanka and Australia in Colombo on Tuesday:
N. Dickwella st Carey b Maxwell 1
P. Nissanka c Carey b Marsh 13
K. Mendis b Cummins 14
D. de Silva c Maxwell b Marsh 60
C. Asalanka c Finch b Cummins 110
D. Shanaka run out (Marsh/Carey) 4
D. Wellalage c Warner b Kuhnemann 19
C. Karunaratne lbw b Kuhnemann 7
W. Hasaranga not out 21
J. Vandersay run out (Cummins/Carey) 0
M. Theekshana run out (sub Swepson) 0
Extras (lb2, nb1, w6) 9
Total (all out, 49 overs) 258
Fall of wickets: 1-5 (Dickwella), 2-26 (Mendis), 3-34 (Nissanka), 4-135 (de Silva), 5-150 (Shanaka), 6-207 (Wellalage), 7-222 (Karunaratne), 8-256 (Asalanka), 9-257 (Vandersay), 10-258 (Theekshana)
Bowling: Hazlewood 10-0-45-0 (w1), Maxwell 8-0-49-1 (w1), Kuhnemann 8-0-56-2 (w1), Cummins 9-1-37-2 (w2), Marsh 7-1-29-2 (nb1), Green 5-0-27-0, Labuschagne 2-0-13-0
Australia (target 259)
D. Warner st Dickwella b de Silva 99
A. Finch lbw b Karunaratne 0
M. Marsh c de Silva b Wellalage 26
M. Labuschagne lbw b Vandersay 14
A. Carey c Wellalage b Hasaranga 19
T. Head b de Silva 27
G. Maxwell lbw Theekshana 1
C. Green b Vandersay 13
P. Cummins lbw b Karunaratne 35
M. Kuhnemann c Asalanka b Shanaka 15
J. Hazlewood not out 0
Extras (lb1, nb1, w3) 5
Total (all out, 50 overs) 254
Fall of wickets: 1-3 (Finch), 2-66 (Marsh), 3-101 (Labuschagne), 4-131 (Carey), 5-189 (Head), 6-190 (Maxwell), 7-192 (Warner), 8-223 (Green), 9-240 (Cummins), 10-254 (Kuhnemann)
Bowling: Karunaratne 5-1-19-2 (w1), Theekshana 10-1-40-1, Hasaranga 10-0-52-1, Wellalage 5-0-29-1 (nb1, w1), de Silva 10-0-39-2, Vandersay 7-0-40-2 (w1), Asalanka 1-0-7-0, Shanaka 2-0-27-1
Result: Sri Lanka won by four runs