What was Christian Doppler's nationality?

Christian Doppler was Austrian. He was born in 1803 in Salzburg, then part of the Austrian Empire’s broader historical world, and became an Austrian mathematician and physicist.

Doppler is remembered for formulating the principle now called the Doppler effect. In 1842, he argued that the observed frequency of a wave changes when the source and observer move relative to one another. The idea applies to sound, light, radio signals, and astronomical observations.

A common mix-up is to identify Doppler by the modern country where he was born rather than by his nationality. Salzburg is in present-day Austria, and Doppler is consistently described as Austrian. His professional life also included work in Prague and Vienna, but those locations do not change the answer to this question.

Doppler died in Venice in 1853, at the time within the Austrian Empire. His name later became attached to technologies including weather radar, medical ultrasound, and astronomical measurements of stellar motion.