Michael Phelps reveals he secretly wed partner ex-Miss California Nicole Johnson

Olympic swimming champion Michael Phelps has revealed that he secretly married his partner, former Miss California, Nicole Johnson.

"I've been married for a while - a couple of months," he said in a Facebook video post.

"I had to keep it secret from you all - I had to keep it hush-hush from you guys.

"Nicole and I are married. We are officially married and now we are getting a chance to just hang out."

Michael Phelps pictured with his son Boomer. Credit: Reuters

Phelps, who is the most decorated Olympian of all time with 28 medals, tied the knot in Paradise Valley Arizona on June 13.

He revealed his engagement to Johnson in February 2015.

The former Miss USA contestant posted a photo on Instagram of herself, Phelps and their five-month-old son Boomer in casual clothes on the day of the wedding with the following caption: "Such a memorable night with my lil fambam."

Phelps, 31, competed in the Rio 2016 Olympic Games this summer, where he won the 23rd gold medal of his career.

He announced that the Rio 2016 would be his last Olympic Games.