Jeannette Josephina Maria "Netti" Witziers-Timmer (née Timmer, 22 July 1923 – 25 January 2005) was a Dutch sprint runner. In 1944 she was a member of the Dutch teams that set world records in the 4×110 yard and 4×200 m relays. Two years later she won a European title, and in 1948 an Olympic gold medal in the 4×100 m relay. The 1948 Dutch relay team was remarkable in that all its members were married and had children.
Witziers-Timmer died on January 25, 2005. She was 81 at the time of her death.