|Ospreys (14) 26|
|Tries: Biggar, Matavesi, Grabham 2 Cons: Biggar 3|
|Ulster (21) 46|
|Tries: Jackson, Best, Trimble, Henry, Olding, van der Merwe Cons: Jackson 5 Pen: Jackson 2|
Ulster set up a Pro12 semi-final with Leinster and ended the Ospreys' hopes of a European Champions Cup spot with a convincing win at the Liberty Stadium.
Scores from Paddy Jackson and Rory Best plus an opportunist Andrew Trimble try left Ulster 21-14 up at the break.
The Ospreys' first-half scores came from Dan Biggar and Josh Matavesi.
Chris Henry was gifted Ulster's fourth try and after two Tom Grabham scores, Stuart Olding and Franco van der Merwe added late tries for the visitors.
Ulster's win means they will face Leinster in the Pro12 semi-finals at the RDS in Dublin on Friday, 20 May. Ulster were beaten by the Dublin outfit in the last four in 2011 and 2014, as well as the final in 2013.
The defeat ends a poor Pro12 campaign for former champions Ospreys as they fail to qualify for the top-tier European club competition for their first time.
Ospreys run out of steam after promising start
Biggar's 12th-minute try under the post was just reward for the Ospreys' early attacking endeavour but Ulster hit back with two tries in 10 minutes as both Jackson and Ireland skipper Best were easily able to breach the opposition defence.
Matavesi brushed off Best to score a levelling try in the 35th minute but Ulster regained the lead in first-half added time as Trimble gathered his own seemingly harmless kick ahead to score after the cruellest of bounces had unhinged Rhys Webb.
After his successful three first-half conversions, another penalty from the in-form Jackson increased Ulster's lead to 24-14 following the restart before a piece of Henry opportunism secured his team's bonus point.
The Ospreys appeared to have a five-metre scrum under control but the Ireland flanker reached through a ruck to get the touchdown after Webb had rolled the ball back onto his own line.
Despite prolonged home protests, TMO Derek Bevan confirmed the try.
As scrum and line-out difficulties caused Ulster's performance to become somewhat ragged, replacement Grabham scored two late Ospreys tries but both efforts were quickly replied to by scores from Olding and lock van der Merwe.
Ospreys: D Evans, B John, O Watkin, J Matavesi, E Walker, D Biggar, R Webb (captain): N Smith, Sc Baldwin, D Arhip, R Bernardo, R Thornton, D Lydiate, S Underhill, J King
Replacements: S Otten, G Thomas, A Jarvis, J Bearman, O Cracknell, B Leonard, S Davies, T Grabham
Ulster: J Payne; A Trimble, L Marshall, S McCloskey, C Gilroy; P Jackson, R Pienaar; C Black, R Best (capt), R Lutton, P Browne, F van der Merwe, I Henderson, C Henry, S Reidy.
Replacements: R Herring, K McCall, A Warwick, R Diack, R Wilson, P Marshall, S Olding, D Cave.
Referee: Marius Mitrea (Italy)
Assistant Referees: Leighton Hodges, Gwyn Morris
Citing Commissioner: Dennis Jones (WRU)
TMO: Derek Bevan