South Africa international Marcell Coetzee will leave the Sharks at the end of the 2016 Super Rugby season to join Irish province Ulster.
Back-row forward Coetzee, who boasts 28 South Africa caps at the age of 24 but was overlooked for last year's Rugby World Cup, has agreed a three-year deal with the Pro12 side.
Ulster director of rugby Les Kiss said: "It is a major coup for us to sign a player of Marcell's quality and experience. His age profile, positional versatility, leadership ability and character were some of the key ingredients as to why he was such an important target for us.
"He has played most of his international rugby between six and seven, but he has also played a huge amount at number eight, where we feel he could have a big impact for Ulster.
"That versatility is absolutely vital for us, as not only can Marcell be hugely effective across the three positions, but this can also accommodate the development of a number of our home-grown Irish-qualified players."
Gary Gold, the Sharks' director of rugby, indicated the club were unable to compete with the financial package offered by Ulster.
"Marcell has made a significant contribution in recent seasons but we understand the appeal of the huge salaries on offer in Europe," said Gold.
"He will be missed, and yet his departure will create new opportunities for the group of outstanding loose forwards emerging in our squad.
"Marcell is fully committed for Super Rugby, and will captain the Sharks team in the match against Toulouse [on Thursday]."