Selena Gomez. Picture: Instagram

Selena Gomez has posted a touching tribute to her close pal Taylor Swift in honour of her 28th birthday.

The 'Look What You Made Me Do' singer turned 28 on Wednesday, and her special day didn't go unnoticed by her celebrity best friend Selena, who took to Instagram to tell her pal she is "glad" she was born.

Posting an adorable video of the pair making faces at the camera before laughing, 25-year-old Selena wrote: "I'm glad you were born. You write all the thoughts some aren't able to articulate. (ME!) Thank you for giving a voice to this world that is authentic and inspiring. I wish some knew how big your heart actually is.. it's fierce, bold and freaking wild with light. I'm glad you protect that. Love you @taylorswift (sic)"

Selena and Taylor have been showbiz pals for almost a decade, and the pair are no strangers to sharing their love for one another on social media.

In honour of the 'Bad Liar' singer's 24th birthday in July 2016, Taylor posted an old photograph of the pair posing together whilst forming the shape of a heart with their hands. 

She captioned the snap: "Going through old pictures today, because @selenagomez just turned 24! I can't imagine my life without you, Selena. HAPPY BIRTHDAY! (sic)."

Meanwhile, Selena has also credited the blonde star as one of her closest pals. 

Speaking previously about her intimate friendship group, she said: "I can count on one hand the people I could call and who would be there for me.

"Taylor is one of the greatest people. When I split with my first boyfriend and I was really sad about it, she flew into town with homemade cookies and a bunch of junk food. To this day, if I called her, she would do the same thing, despite being one of the busiest people in the world."