The 26-year-old heads to the Kingspan Stadium from Dublin on a two-year deal, having made 95 appearances for Leinster.
He admitted it had been a tough decision to switch to a Guinness PRO14 rival, but the opportunity to develop as a player was too good to turn down.
Murphy said: “It’s been an incredibly hard decision to leave Leinster, where I have made some great friends and enjoyed some fantastic times, but I am excited by the prospect of moving north and linking up with some familiar faces.
“Having considered my options at length, I realise that this represents a great opportunity for me to challenge for a position at Ulster and hopefully become a more regular feature in the national set-up.
“Ulster is building a strong squad for next season and I’m really looking forward to the new challenge. However, I am fully focused on contributing as best I can for Leinster for the remainder of the current campaign.”
Murphy has 18 international caps to his name, most notably scoring a try in Ireland’s historic win over New Zealand in Chicago last year.
Since then he has had to be patient after suffering from a torn ACL, but now back up to full fitness, he made his Test return in November.
And Ulster director of rugby Les Kiss was thrilled at the acquisition.
He said: “Jordi has been on our radar for the past 12 months and it took a lot of hard work between his agent and (Ulster operations director) Bryn (Cunningham) to get this completed. Unsurprisingly, there was a lot of interest in Jordi and we are really pleased that he has chosen to ply his trade here in Belfast.
“The acquisition of Jordi for next season is great news for everyone connected with Ulster Rugby and I believe this move will greatly benefit both parties.
“The increased investment in our academy forwards is starting to pay off and five of those in our current system – Nick Timoney, Adam McBurney, Aaron Hall, Greg Jones and Matthew Dalton – have played for the senior team already this season. That’s another positive sign for the future of rugby in Ulster.”
Murphy will reunite with Marty Moore, the former Leinster prop who is heading to Ulster from Wasps in the summer.
And Leinster head coach Leo Cullen also paid tribute to Murphy’s contribution to the province.
He said: “Jordi is a hugely talented player and a very popular member within our squad.
“It is to his enormous credit that he has come back as strong as he has from his knee injury last year in Ireland’s famous win over the All Blacks in Chicago.
“We respect Jordi’s decision to move and everyone at Leinster wishes him the very best with his future.”
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