Heinrich Friedrich Siedentopf (1 December 1906 – 28 November 1963) was a German astronomer and physicist.

He was born in Hannover. In 1930, he became an assistant to Heinrich Vogt, then joined the national observatory in Heidelberg. Between 1940–46 he was a professor of astronomy at the University of Jena, and director of the observatory. In 1949, he was a professor at the University of Tübingen,^[1] where he later died of a heart attack.

Professor Siedentopf published a total of 146 papers and a textbook. He studied cosmology, stellar convection,^[2] photometry and the zodiacal light.^[3] In 1934, he developed an adjustable iris for the Stetson-Schilt photometer, allowing the observer to adjust the light level directed at the astronomical plate.^[4][5]

Siedentopf crater on the Moon^[6] and the main belt asteroid 5375 Siedentopf were named after him.