American singer Gwen Stefani turned 51 on Saturday (Oct 3), and her boyfriend, country singer Blake Shelton, lost no time in expressing his love for her.

Shelton, 44, took to social media that day and wrote: "It's a special day for a special lady in my life. Happy birthday @gwenstefani, I'd write a song for you every single day if I could."

His post also showed a post of them from their music video Happy Anywhere, where she is seen cosying up to Shelton in a corn field.

Meanwhile, Stefani, the lead vocalist of the band No Doubt, also posted a black-and-white baby photo of herself on Instagram, thanking everyone for their birthday wishes.

Shelton and Stefani met as coaches on singing-competition show The Voice and went public with their relationship in November 2015 after rumours of them dating surfaced online.

He was previously married to fellow country singer Miranda Lambert, 36, from 2011 to 2015, while she was married to English singer Gavin Rossdale, 54 for nearly 14 years until 2016.

Stefani and Shelton bought their first home together in California earlier this year, although she disclosed that she had been spending time at his ranch in Oklahoma with her three sons with Rossdale during the coronavirus pandemic.

The couple are currently preparing for the upcoming 19th season of the singing competition The Voice with their fellow coaches, singers John Legend and Kelly Clarkson.