Jaroslav Mareš (28 December 1937 in Brno, Czechoslovakia – 5 May 2021, Prague) was a Czech biologist, traveller and writer.
He graduated from The University of Economics in Prague, getting a degree of Ing (he studied international business).
He visited 85 countries and organised several expeditions for research of cryptids, such as Kongamato (for this he was offered the membership of the International Society for Cryptozoology which he accepted), Nandi bear, Megalania prisca, Bigfoot, Yeti, Nessie, Ogopogo, Champ, megalodon, Lusca, Ambazombi and others.
In 1978 he organised an expedition to the tepui which probably inspired Sir Arthur Conan Doyle for writing The Lost World (a book based on stories told to Doyle by Colonel Percy Fawcett).
He also studied dinosaurs (he visited most of the famous fossil sites, such as Nemegt in Mongolia, Tendaguru in Tanzania, Red Deer in Alberta, and other localities in Utah, Colorado, Montana and Patagonia) and corresponded with the world-leading palaeontologists.