A joint statement by Musk and Riley says they have both decided to end their marriage and will remain friends.
They say they have been separated for six months.
Riley and Musk divorced in 2012 after first marrying in 2010, but re-married 18 months later. The second divorce petition filed by Musk was never finalized.
Musk co-founded PayPal and has gone on to start SpaceX and Tesla Motors.
Riley appeared in ‘Pride & Prejudice’ and ‘Inception’ and wrote and directed her first feature film, ‘Scottish Mussel,’ in 2014.
The couple has no children.
Musk has five sons with his former wife Justine, to whom he was married from 2000-2008; a set of twins, Griffin and Xavier, born in 2004, and a set of triplets, Damian, Saxon, and Kai aged born in 2006, conceived using IVF after their eldest child Nevada died of SIDS.