Ravenna is the second big name to leave Leeds at the end of the season.
Brazilian winger Ravenha, who played a central role in Leeds United's retention of their Premier League spot last season, is preparing to sign for Barcelona after the clubs agreed on the deal in principle on Wednesday.
The 25-year-old will cost the Catalans 55 million euros ($55.3 million), with a possible bonus of 15 million euros, and will sign a five-year contract.
"Barcelona and Leeds United Football Club have reached an agreement in principle for the transfer of Rafael Dias Piloli Rafinha, pending the processing of the player," read a statement on Barcelona's website.
Barcelona said they were buying: "A great winger in one against the other, defense is an essential part of their game."
Raphinha spent two seasons at Elland Road, scoring 17 goals and providing 12 assists after signing him from Ligue 1's Rennes for £17m, set to cut the French side's transfer fee.
Raphinha, who is two years behind on her contract, became a fan favorite and secured a permanent place in his hearts when he scored a penalty in last season's 2-1 win over Brentford in the final. They stood in English first class.
Leeds manager Jesse Marsh, who replaced the sacked Marcelo Bielsa at the end of February, praised Praveenha, who was impressed with the dedication he showed in the battle to keep them together.
"If you think about a youngster who was guaranteed a reduced transfer fee (apparently £25m), 100% to Barcelona if we go down.
"And then you see the performances and the commitment that he had to make sure the club stayed awake, I think it would be difficult for a 25-year-old to put that pressure on like he did."
"We are very grateful."
Barcelona was able to spend after alleviating its huge financial problems by selling 10% of its television rights to Sixth Street of America for 25 years at the end of June at a cost of around €207.5m.
Raphinha, who has been capped nine times, is Barcelona's third signing at the end of the season after Ivory Coast defender Frank Kessie from AC Milan and Danish defender Andreas Christensen from Chelsea.
Raphinhais the second big name to leave Leeds at the end of the season, with England midfielder Calvin Phillips leaving for champions Manchester City for £45m.
Despite this, Leeds have not been quiet in the transfer market by buying six players in their bid to avoid a repeat of last season's frustrating experience.
Among them is Colombian winger Luis Sinister, who last week signed for £21.4m from Dutch club Feyenoord when Rafinha's departure became inevitable.