Olivia Rodrigo rang in her 22nd birthday in the celeb-favorite swimsuit of the moment ... for the camera in a plunging, red one-piece bathing suit and a gray baseball cap, keeping her pigtail ...

Can’t wait to make this one-piece my whole personality this summer. And if you’re looking for more swimsuit inspo ahead of spring break, we’ve got you covered: ...

In addition to Rodrigo’s cherry color, the plunging maillot currently comes in 14 other shades ranging from neutrals like black, white and gray ... fitting swimsuit I own,” one buyer wrote.