Chris Pratt and Anna Faris. Picture: Bang Showbiz

Chris Pratt and Anna Faris reportedly "shocked" their friends when they announced they were ending their marriage.

The couple - who share four-year-old son Jack -called time on their romance after eight years of marriage and their pals didn't even realise anything was wrong between the two.

A source said: "It's just insane. Anna and Chris were so in love."

Talking about the rumours Chris could have cheated on Anna, the insider added to Entertainment Tonight: "It isn't true. Chris wanted Anna on [set with him] whenever possible. He never wanted her to have a reason to worry."

Chris and Anna announced they were "legally separating" in posts on their social media on Sunday evening.

In a statement posted on Chris' Facebook page, he said: "Anna and I are sad to announce we are legally separating. We tried hard for a long time, and we're really disappointed. Our son has two parents who love him very much and for his sake we want to keep this situation as private as possible moving forward. We still have love for each other, will always cherish our time together and continue to have the deepest respect for one another."

Only a few months ago, Chris was gushing about his wife Anna. 

Speaking back in late April at his Hollywood Walk of Fame star ceremony, he said: "I want to thank my wife Anna, I love you. You've given me so much. You gave me the greatest star in the galaxy in my little boy, I love him and I love you.

"We have bonded to make this molecule that is more important to me than air or water, and without it none of this means anything to me. With every challenge, with every day, week, month, decade, we become more bonded."