Jessica Biel and Justin Timberlake. Picture: Reuters
Justin Timberlake and Jessica Biel have exchanged romantic messages on Instagram as they celebrated their fifth wedding anniversary.

The 'Trolls' star hailed himself the "luckiest man in the world" for being wed to 'The Sinner' actress - the mother of his two-year-old son Silas - and marked five years since they tied the knot by sharing a video of himself singing Donny Hathaway's 'A Song for You'.

The song holds special significance for the couple as it was the first piece of music they danced to as husband and wife.

Justin wrote on Instagram: "#TBT to a late night freestyle session on a break in the studio - YES I've been back in the studio cooking! But, today is even more special for me because five years ago, on this day, I became the luckiest man in the world when I exchanged vows with my best friend. This song was our first dance. 

"To my beautiful @jessicabiel: You have taught me so much about what a true love means.

"I can't put into words what these last five years have meant to me, so ... 'Listen to the melody 'cause my love is in there hiding... ' #Happy5thAnniversaryWifey #AsongForYou (sic)"

He also shared an intimate picture of the couple kissing with his 46.4 million followers.

Jessica replied on her own Instagram account: "My tender heart is yours, now until forever."

My tender heart is yours, now until forever.

A post shared by Jessica Biel (@jessicabiel) on

She also posted a comedy video of the pair dancing along to the car stereo, with a flower-ear filter on, and wrote: "How lucky am I? Even if he's initially skeptical, he always gets extra for me. #5(sic)"

Jessica, 36, previously admitted meeting 35-year-old Justin had changed her priorities away from her career.

She said: "I didn't grow up dreaming about having kids and having a family. I was so focused on my career and so focused on my selfish existence, haha, but I think meeting my husband inspired me.

"One day I just woke up and knew it's what I wanted to do and it's been the hardest, greatest thing ever and I wouldn't give it up for the world."