Rudolf Franz Flesch (Vienna, 8 May 1911 – New York, 5 October 1986) was an Austrian-born naturalised American author (noted for his book Why Johnny Can't Read), and also a readability expert and writing consultant who was a vigorous proponent of plain English in the United States.
He created the Flesch Reading Ease test and was co-creator of the Flesch–Kincaid readability test.
Flesch advocated use of phonics rather than sight reading to enable students to sound-out unfamiliar words.