Ejnar Hertzsprung (Danish: [ˈɑjnɐ ˈhɛɐ̯tsˌpʁɔŋ]; 8 October 1873 – 21 October 1967) was a Danish chemist and astronomer born in Copenhagen. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram. His wife Henrietta (1881–1956) was a daughter of the Dutch astronomer Jacobus Kapteyn. Hertzsprung died in Roskilde in 1967. The asteroid 1693 Hertzsprung was named in his honour.