Centre Will Addison and back row Jordi Murphy have committed to Ulster Rugby for a further two years.
Jacob Stockdale, Louis Ludik and Sean Reidy will also remain at the Kingspan Stadium as head coach Dan McFarland named his squad for the 2020-21 season.
The province's two new signings are Ireland fly-half Ian Madigan and former New Zealand scrum-half Alby Mathewson.
Nathan Doak, son of of former Ulster player and coach Neil, has joined the club's Academy squad.
Of the 41 fully contracted players and two development players, 39 of are Irish qualified.
McFarland's men have not played since beating Cheetahs at Kingspan Stadium on 22 February because of the coronavirus outbreak, and it remains unclear when Pro14 and European Champions Cup rugby will be able to return.
The club announced last month that 70% of staff, including all players and coaches, were placed on furlough.
"Our desire to build on the successes of this season to-date is evidenced in our strong investment in talent from the current squad," said McFarland.
"Although it's an uncertain time for rugby, and all sport, I am confident our selection will stand us in good stead for when we are able to safely start the new season.
"Once again, the chosen line-up of players shines a light on the indigenous talent nurtured through the Academy by Kieran Campbell and his staff - and the role which it, along with the province's clubs and schools, continues to play in securing the future of Ulster Rugby.
"I would also like to take this opportunity to thank the players who are moving on from the squad. This includes Clive Ross, who earned 73 caps since joining the province on a development contract in 2014, along with 21-capped Angus Kernohan, and Zack McCall.
"Looking to the future, we look forward to welcoming the new additions to the squad, who are set to bring their own unique skills and talent, as we move towards a time when the 2020/21 season can kick-off."
Matty Rea is another player who remains in the squad, while Stewart Moore has been awarded a new three-year deal which will see him graduate from the Academy to spend one year as a development player, before being upgraded to a senior professional contract for the following two seasons.
Joining Doak in the Academy are Reuben Crothers, Ben Carson, Lewis Finlay, Cormac Izuchukwu and James McCormick.
Full Ulster squad: Will Addison, John Andrew, Robert Baloucoune, Billy Burns, Sam Carter, Marcell Coetzee, John Cooney, Angus Curtis, Matt Faddes, Craig Gilroy, Iain Henderson, Rob Herring, James Hume, Bill Johnston, Greg Jones, Ross Kane, Michael Lowry, Louis Ludik, Rob Lyttle, Ian Madigan, Luke Marshall, Alby Mathewson, Adam McBurney, Kyle McCall, Stuart McCloskey, Jack McGrath, Gareth Milasinovic, Marty Moore, Stewart Moore, Jordi Murphy, Alan O'Connor, David O'Connor, Eric O'Sullivan, Tom O'Toole, Marcus Rea, Matty Rea, Sean Reidy, David Shanahan, Jonny Stewart, Jacob Stockdale, Nick Timoney, Kieran Treadwell and Andrew Warwick.