Betfair and Paddy Power are set to merge in a deal that would create one of the world's biggest online betting and gaming companies.
Final details are still being worked out but the companies said the deal had "compelling strategic logic" and boosted their market position.
Paddy Power shareholders would own 52% of the combined business, with Betfair investors owning the remaining 48%.
The combined business would have with annual revenues of some £1.1bn.
Shares in Betfair soared 18% to £30.72 on Wednesday, while Paddy Power jumped more than 15% in Dublin.
"Discussions remain ongoing regarding the other terms of the possible merger," a statement said on Wednesday.
If the deal goes ahead, Breon Corcoran, boss of Betfair, would become chief executive of the combined group, while his counterpart at Paddy Power, Andy McCue, would become chief operating officer. Industry mergers
The combined company plans to retain the "distinctive and complementary" Betfair and Paddy Power brands in Europe.
Gary McGann, chairman of Paddy Power, is expected to become chairman.
Shareholders in Paddy Power would receive a special dividend of €80m.
Based on their closing prices on Tuesday, Betfair was worth £2.4bn and Dublin-listed Paddy Power was worth €3.4bn (£2.5bn).
There has been a flurry of merger activity in the gambling sector in recent months.
In July online gambling firm 888 Holdings won a takeover battle for rival Bwin.party in a cash and stock deal valued at about £898m.
The two companies had been in discussions since the middle of May.
Ladbrokes and Gala Coral also recently sealed an all-share merger, creating a £2.3bn betting group.
The strategic imperative for this merger of 2 giants is pretty clear to me (I used to be a management consultant so I know about these things, trust me)
Paddy Power is desperate to get hold of Betfair's unparalleled IT expertise and robust systems. In particular they want this merger to go through before the clocks go back as Betfair's ability to change the clock is legendary.
I, for one, see this strategic move as equivalent (at least) to Marks and Spencer's, or even Tesco's, bold move into the North American space.
The strategic imperative for this merger of 2 giants is pretty clear to me (I used to be a management consultant so I know about these things, trust me)Paddy Power is desperate to get hold of Betfair's unparalleled IT expertise and robust systems. I
when you've been a high powered management consultant you just have to use words like strategic imperatives, robust systems, space, change initiatives, emerging markets, challenges ... ooohh there's hundreds of them.
Happy to share this with you ... that's mememe, a leader not a laggard
No Leopard,when you've been a high powered management consultant you just have to use words like strategic imperatives, robust systems, space, change initiatives, emerging markets, challenges ... ooohh there's hundreds of them.Happy to share this wit