Shawn Mendes Goes Instagram Official with Girlfriend Bruna Marquezine

Shawn Mendes just went public with his relationship with girlfriend Bruna Marquezine ... ringing in her birthday with a doting post on Instagram!

Check it out -- the pop star celebrated Bruna's 31st birthday with a sweet caption in which he called her "a light and a mãe in every room you walk into." He went on, "Not to be tooooo sappy but you’ve truly changed my life and I am so so grateful for you."

He even publicly declared his love for her in Portuguese, writing ... "Eu te amo muito muito muitoo" -- which translates to "I love you so, so, so much."

Alongside his romantic caption, Shawn shared a video of the Brazilian actress being welcomed into a room full of cheering kids at Casa Amarela Providência, a cultural, educational, and arts center in Brazil. Other videos showed Marquezine singing and dancing with the children as they seemingly sang “Happy Birthday” to her, plus Shawn smiling with some of the kids.

This is a huge step for the lovebirds -- they were first rumored to be dating back in December ... and they’ve been seen together in the States and Bruna's home country of Brazil several times.

We caught them packing on the PDA on the beach in Brazil back in March, for instance ... but this is the first public confirmation of their relationship.

As you know, Shawn previously dated Camila Cabello off and on between 2019 and 2023. He was also publicly linked to Sabrina Carpenter in February 2023 -- just before he briefly rekindled with Camila.