"By Your Side" is a song by Scottish DJ and producer Calvin Harris featuring English singer and songwriter Tom Grennan, released on 4 June 2021 via Sony Music.

On 4 June 2021, Grennan shared a video on Twitter, captioning it "this is going to be the summer we've all been waiting for.

"[4] In an interview with Apple Music 1's Zane Lowe, Harris said: "The first thing is I liked Grennan's voice a lot.

"[6] Ellie Mullins of website We Rave You described "By Your Side" as the most essential summer anthem for 2021, writing that "Grennan's influence is heard and not just through the vocals either but also through the fun, upbeat guitars that can be found throughout" and "Harris is on top form with upbeat productions and synths that beg to be danced along to".

It was described by Jason Heffler of EDM.com as "kaleidoscopic" and a "bubbly audiovisual project that ties in perfectly with the sun-kissed tune".