Tennis Star Ben Shelton Pens Sweet Birthday Note For Trinity Rodman, 'I Love You'

Ben Shelton gave a special shoutout to his soccer star girlfriend, Trinity Rodman, on Tuesday ... telling the world how much he loves her on her 23rd birthday.

The No 13-ranked tennis pro took to Instagram to deliver his romantic note ... saying, "Happy birthday beautiful girl. I love you."

Shelton published a pair of pics to go along with his mushy words -- a steamy shot of them moving in for a kiss, and another snap of the Washington Spirit forward's birthday dress.

The comment section was flooded with approval ... from North Carolina Courage midfielder Ashley Sanchez to Sloane Stephens, who called the athletes a pair of "cuties."

Shelton and Rodman -- yes, Dennis' daughter -- took their relationship public back in March ... and it's been nothing but sweet content ever since.

They "hard-launched" their romance with an elevator shot ... showing Rodman giving Shelton a kiss on the cheek.

Frances Tiafoe initially took credit as the matchmaker who put them together ... something Shelton later laughed off and denied.

But regardless of how they linked up, it's clear they're doing great!!