Billie Eilish is a Harry Styles stan… duh.

On Sunday (March 14), the Fine Line singer kicked off the 2021 Grammy Awards with a performance of his hit single “Watermelon Sugar,” and he received some side stage support from the 19-year-old singer.

Styles' lime green feather boa and black leather suit had Eilish — who grooved from her soundstage with brother Finneas — totally heart-eyed, naturally.

See the adorable moment captured, below.

The onstage love fest was mutual, though, as the former One Direction member cheered Eilish later on, whistling as she took the stage for a performance of the Grammy-nominated track “Everything I Wanted.”

This year, Eilish is nominated for Song of the Year, Best Pop Solo Performance, Song Written for Visual Media and Record of the Year. In 2020, the “Bad Guy” singer went home with five awards, including Album of the Year.

Styles is nominated for three awards, including Best Pop Vocal Album, Best Pop Vocal Album and Best Music Video.

Harry Styles at the 2021 Grammys

See some reactions to Eilish and Styles' sweet Grammys performance interaction, below.

Most Memorable Grammys Moments Ever

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