|Men's Artistic Gymnastics|
|Competitor for Germany|
|Gold||1896 Athens||Team parallel bars|
|Gold||1896 Athens||Team horizontal bar|
Flatow competed in the parallel bars, horizontal bar, vault, pommel horse, and rings individual events. He won no medals, unlike his cousin and teammate Alfred Flatow. However, both were members of the German team that competed in the two team events, for parallel bars and the horizontal bar. As Germany won both those events (the horizontal bar unchallenged), Gustav earned two gold medals. He also competed at the 1900 Summer Olympics in Paris, but without winning medals. He retired from gymnastics to manage his textile company, which he founded in 1899.
After the Nazi takeover in Germany in 1933, he had to flee to the Netherlands. On New Year's Eve 1943 he was jailed, and in February 1944 he was deported to Theresienstadt concentration camp, where his cousin had already died in 1942. Less than one year later he starved to death there at the age of 70. He lost up to about 20 kg.
In 1986 journalists discovered his urn, which is now entombed in Terezín near the site of the concentration camp.
In 1997 Berlin honoured Alfred and Gustav Flatow by renaming the Reichssportfeldstraße (a lane) near the Olympic Stadium to Flatowallee (Flatow-avenue). There is also the Flatow-Sporthalle (sports hall) at Berlin-Kreuzberg with a commemorative plaque for both. The Deutsche Post issued a set of four stamps to celebrate the 100th anniversary of the modern Olympic games. One of the stamps honors the Flatows.
- Schaffer, Kay; Smith, Sidonie (2000). The Olympics at the Millennium: Power, Politics, and the Games. Rutgers University Press. pp. 60–62. ISBN 978-0-8135-2820-5.