"Happy Bday to my first partner in crime and the FIRST QUEEN OF THE HOUSE," Justin, 33, wrote alongside. "We have been through so much together and I love you more than words can begin to describe."
Justin Timberlake celebrated his mum's birthday was a throwback photo
He continued: "Everything I am and continue to strive to be is because of you. I love you Momma! #UandMeVsAnybody."
The singer is known to have a very close bond with his mother, who divorced Justin's father Randall Timberlake – a Baptist church choir leader – when their son was three years old. Lynn went on to find love again, marrying Paul Harless two years later.
Justin often brings his mum along to red carpet events, including the Academy Awards in 2011, and the MTV VMAs in 2013. He spoke about their connection during an interview with Rolling Stone magazine in 2013.
"We have a very special relationship. She's been my best friend since I figured out who I wanted to be," the singer said. "She's always been there beside me, and I think that's part of my problem with girls. You keep searching for somebody as good as your mother, and that's a losing battle."
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Of course, since then, Justin has found someone special to share his life with – wife Jessica Biel. The couple, who tied the knot in October 2012, are also expecting their first child together, leaving Lynn especially excited for the year ahead.
"Justin's mum is so excited about the baby," an insider told E! News, adding that mummy-to-be Jessica is "feeling really good".