Ben Affleck has announced the name of his baby boy.

The actor and wife Jennifer Garner welcomed their son, Samuel Garner Affleck into the world on Monday.

In a statement released on his Facebook page, the Hollywood actor couldn't be prouder to let the world know of the new addition to his family.

"We are happy to announce on February 27, Jennifer gave birth to a healthy baby boy, Samuel Garner Affleck," the Oscar winner posted.

The new bundle of joy will be the younger sibling to older sisters Violet, six, and Seraphina, three.

The couple, both 39, have been married for six-and-a-half years and live in Brentwood, California.

Ben recently spoke about how his children inspire him to do good things in the world.

"I got to the point in my life where I felt like I had been very fortunate," he told People magazine.

"And I wanted to do something more with my life than just make movies and try to make money. I wanted to do something that was important to me in other ways and would serve as an example to my kids."

Ben founded the Eastern Congo Initiative two years ago and recently made his eighth trip to the war-torn area.

The organisation will help support other groups to rebuild the region and give former child soldiers health care and hope for a better life.