We're told Pratt filed the documents Friday, citing irreconcilable differences as the reason for ending the marriage.
Even though the "Guardians of the Galaxy" star was the first to file, he didn't do it without his estranged wife's knowledge. Faris filed her response to Pratt's documents at the same time, so it's clear there was some coordination between the two.
As for their five-year-old son Jack, they both are seeking joint custody. We're told both Pratt and Faris are committed to co-parenting their son in the healthiest way possible.
A source close to the couple tells us this will be a "very clean" divorce, and not a messy Hollywood breakup.
We're told the two will have a private settlement, and have been in negotiations for a "very simple separation of assets."
The ex-couple had been married for eight years, they announced their separation in August.