Josef Lošek was a Czechoslovak competitive cyclist who was active during the early 1930s. In 1933 Lošek won his first national title, before finishing second a year later and winning his second title in 1936. These performances earned him a place on the Olympic team for the 1936 Berlin Games. In the road race he was in the main peloton of more than 20 riders who tied for 16th place, just three seconds behind the winning time. One year later Lošek finished second in the Praha–Karlovy Vary–Praha, the longest amateur race in Europe at the time.