Is this the best celebrity photobomb ever?

Who is the mystery woman in the background? Photo: Instagram Source: Supplied

RYAN Phillippe is the victim in one of the best celebrity photobombs ever.

The actor went for a walk in West Hollywood a couple of days ago and did his best to look cool in front the of paparrazi.

But unbeknowst to him, a woman in the background took it upon herself to make the picture a little "sassier".

39-year-old Phillippe posted the photo on his Instagram with the caption, "Got papped w/ @bwash & that lady."

But it turns out 'that lady' just happens to be Sarah Hudson, a singer who has Goldie Hawn and Aerosmith's Steven Tyler as godparents and who is first cousins with actor Kate Hudson.

It's great to see a bit of harmless Hollywood fun ... it's not as if Hudson didn't have 'cruel intentions'.