Heinrich Emil Albert Knoevenagel (German pronunciation: [ˈhaɪnʁɪç ˈʔeːmiːl ˈʔalbɛʁt ˈknøːvəˌnaːɡl̩]; 18 June 1865 – 11 August 1921) was the German chemist who established the Knoevenagel condensation reaction.

The Knoevenagel condensation reaction of benzaldehydes with nitroalkanes is a classic general method for the preparation of nitroalkenes, which are very valuable synthetic intermediates.