That’s Jason Isaacs. Um, I looked at some HP screencaps and such and it’s hard to tell bc Lucius Malfoy’s default expression is very un-Marius to me :- There is more to Marius than flowing platinum hair, blue eyes, and a Roman face.

However, it could work, I did find some stellar fanart of him that seemed more Marius-ish:

 ^Bianca et Marius Lucius et Narcissa Malfoy, by Makani

^Bianca? Not Pandora… a servant? et Marius Lucius Malfoy,

by Makani

^Lucius Malfoy by ladunya

^Bianca et Marius Lucius et Narcissa Malfoy, by Makani

^Marius et Pandora Lucius et Narcissa Malfoy, by Makani