The announcement comes just weeks after the Danish player appointed six-times major winner Boris Becker as his coach ahead of the 2024 season.
Luthi, 47, coached Federer from 2007 until the 20-time grand slam champion's retirement in 2022, and also captains the Swiss Davis Cup team.
Roger Federer (left) trains with Severin Luthi in Melbourne ahead of the 2014 Australian Open. (Julian Smith/AAP PHOTOS)
Rune, who is gearing up for the year's opening grand slam event, the January 14-28 Australian Open, has been working in Monte Carlo with Becker after bringing the German on to his team in mid-October.
"Very happy to welcome Severin to my team alongside Boris," Rune wrote on social media, along with a picture of his team.
Rune made two ATP 1000 finals this year, at Rome and Monte Carlo, while his only title came at the Bavarian International in Munich in April.
The Dane also made it to the fourth round of the 2023 Australian Open, where he lost a five-set marathon against Russian Andrey Rublev.
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