|Ulster (3) 8|
|Try: Stockdale Pen: Cooney|
|Ospreys (0) 0|
Jacob Stockdale's last-minute try helped Ulster keep alive their hopes of qualification for the Pro14 play-offs by beating Ospreys 8-0 in Belfast.
John Cooney's penalty gave Ulster a 3-0 half-time lead and winger Stockdale's touchdown was the only other score.
Ulster move to within four points of third-placed Edinburgh in Conference B.
Stockdale's late try denied Ospreys a losing bonus-point but they stay fifth in Conference A and still have hopes of a 2018-19 Champions Cup place.
Ulster revived their ambitions of making the knockout stages by beating Edinburgh away last week and they have yet to play Glasgow at home on 21 April and Munster at Thomond Park seven days later.
This was Ospreys' first defeat in five games and it marked interim head coach Allen Clarke's first visit to the Kingspan Stadium since departing his role as an assistant coach at Ulster last season.
Ulster were the better side in the first half but only had Cooney's seventh-minute penalty to show for their superiority as they turned down other kickable shots at goal on a number of occasions.
Cooney kicked the ball between the posts after a stray Ospreys boot had kicked the ball out of a ruck.
The Irish province then came close to scoring a try two minutes later only for Dan Evans to beat Johnny McPhillips to the touchdown after the out-half put in a grubber kick under Ospreys' posts.
Dan Biggar missed with his 21st-minute penalty attempt, the Welsh side's only kick at goal throughout the game.
Centre Kieron Fonotia touched down for Ospreys on the half hour but, after consultation with the television match official, referee Andrew Brace disallowed the score for a neck roll on Iain Henderson by Alun Wyn Jones in a ruck.
Ulster's response nearly saw man-of-the-match Mattie Rea make the line only for Charles Piutau to be held just short and Ospreys won a penalty to relieve the pressure.
Ulster blew another scoring chance off a five-metre scrum after Louis Ludik had nailed Hanno Dirksen behind his goal line - Piutau's offload missing Stockdale.
However, after Evans was buried by Cooney behind his own line, Ulster won another five-metre scrum after 57 minutes, the result seeing Jeff Hassler yellow-carded for not rolling away.
Again, though, Ulster ignored the three points and went for the scrum, only to give away a penalty when substitute Andy Warwick went off his feet.
Ulster also had a 'try' scrubbed off in the 68th minute when flanker Nick Timoney was adjudged to have lost control of the ball and knocked on as he dived over the line after collecting Luke Marshall's chip.
In the final minute Ireland star Stockdale picked up the loose ball after a stray pass by Biggar and sprinted over the whitewash to score, Cooney off-target with the conversion.
Ospreys coach Allen Clarke said:
"We have no argument with the scoreline, we put in a tremendous defensive effort tonight but we weren't good enough with the ball or at the breakdown and we didn't put them under pressure with the ball in hand.
"We have had a chat about it, we know what we are about and we are in the play-offs, so we may well end up back here."
Ulster: C Piutau, L Ludik, D Cave, S McCloskey, J Stockdale, J McPhillips, J Cooney; C Black, R Best (Capt), R Kane, K Treadwell, I Henderson, M Rea, J Deysel, S Reidy.
Replacements: R Herring, A Warwick, T O'Toole, A O'Connor, N Timoney, D Shanahan, L Marshall, T Bowe.
Ospreys: Dan Evans; Jeff Hassler, Kieron Fonotia, Owen Watkin, Hanno Dirksen, Dan Biggar, Tom Habberfield; Nicky Smith, Scott Otten, Dmitri Arhip, Bradley Davies, Adam Beard, Alun Wyn Jones (capt), Sam Cross, James King.
Replacements: Ifan Phillips, Rhodri Jones, Ma'afu Fia, Lloyd Ashley, Guy Mercer, Matthew Aubrey, Sam Davies, James Hook.
Referee: Andrew Brace (IRFU)
Assistant referees: Joy Neville, John Carvill (IRFU)
TMO: Kevin Beggs (IRFU)