Isoda Koryūsai was a Japanese ukiyo-e print designer and painter active from 1769 to 1790.

Koryūsai was born in 1735 and worked as a samurai in the service of the Tsuchiya clan. He became a masterless rōnin after the death of the head of the clan and moved to Edo (modern Tokyo) where he settled near Ryōgoku Bridge in the Yagenbori area. He became a print designer there under the art name Haruhiro in 1769, at first making samurai-themed designs. The ukiyo-e print master Harunobu died in 1770, and about that time Koryūsai began making prints in a similar style of life in the pleasure districts.

Koryūsai was a prolific designer of individual prints and print series, most of which appeared between 1769 and 1881.

In 1782 Koryūsai applied for and received the Buddhist honour hokkyō ("Bridge of the Law") from the imperial court and thereafter used the title as part of his signature. His output slowed from this time, though he continued to design prints until his death in 1790.