It was discovered by Pierre Méchain in 1781[a] and 29 days later seen again and entered by Charles Messier in his catalogue "of nebulae and star clusters".

[8][9] After the discovery of M100 by Méchain, Charles Messier made observations of the galaxy depicting it as a nebula without a star.

With the advent of better telescopes, John Herschel was able to see a round, brighter galaxy; however, he also mentioned that it was barely visible through clouds.

William Henry Smyth[7] extended the studies of M100, detailing it as a pearly white nebula and pointing out diffuse spots.

Messier 100 is considered a starburst galaxy[10] with the strongest star formation activity concentrated in its center, within a ring – actually two tightly wound spiral arms attached to a small nuclear bar of radius: one thousand parsecs[11] – where star formation has been taking place for at least 500 million years in separate bursts.