Jimmy Kimmel celebrates 'tough' son's birthday after he underwent 2 open-heart surgeries

Kimmel also thanked doctors and nurses who performed two open-heart surgeries.

Jimmy Kimmel is celebrating his son's first birthday -- a monumental occasion for the boy, who was born with a heart defect and has undergone two open-heart surgeries.

"A [year] ago today, God gave us this tough little boy," the late-night talk show host wrote in a caption on Instagram, referencing his son Billy.

"Today, we thank the nurses & doctors at @CedarsSinai & @ChildrensLA who saved his life & those who shared thoughts & prayers," Kimmel, 50, continued.

Kimmel shared that he and his wife, Molly McNearney, welcomed Billy on April 21, 2017, and three days later he underwent his first of two open-heart surgeries.

Billy Kimmel was born with a heart defect. The late-night show host opened up about his son's condition during an emotional monologue, which drew an outpouring of support from fans.

His son's condition placed Kimmel at the center of the national healthcare debate, with the "Jimmy Kimmel Live!" host arguing passionately for coverage for those with preexisting conditions.

"Before you post the nasty Facebook message saying I'm politicizing my son's health problems, I want you to know, I am politicizing my son's health problems because I have to," he said in September.

He went on to use his son's birthday on Saturday to encourage his fans to register to vote.

"We cannot stay quiet. Please wish Billy happy birthday by REGISTERING TO VOTE!," he said, adding a link to Vote.gov.