Maria Aaltje Timmer is a former Dutch speed skater specialising in the sprint distances 500 and 1000 metres, as well as the 1500 metres at the start of her career. She is a three-time Olympic Champion. At the Nagano Olympics in 1998 she won Gold in both the 1000 and 1500 metres. At the Turin Olympics in 2008 she won another Gold medal in the 1000 metres. This made her the first Dutch speed skater to win a Gold medal at two different Winter Olympic Games.
Marianne was born in Sappemeer, The Netherlands. She was married to former goalkeeper Henk Timmer but they are currently separated. She was also previously married to her former coach Peter Mueller.
In 1999 Marianne won the 1000 metres in the World Single Distance Championships and in 2004 she became World Champion Sprint. In addition, Marianne has become Dutch Sprint Champion a record ten times (1997–1999, 2001, 2003–2008). At the Dutch distance championships she won a total of 13 Gold, 14 Silver and 3 Bronze medals in the 500, 1000 and 1500 metres.
On 13 November 2009, at a World Cup speed skating event in Heerenveen, The Netherlands, Marianne broke her heel bone when she crashed after Chinese skater Yu Jing fell in front of her during a 500-metre race. Because of the crash, Timmer was not able to defend her Olympic title at the Vancouver Olympics in February 2010.
Marianne has recently moved into real estate due to a downturn in her motivational speaker, analyst, reporter and speed skate clinic businesses as a result of the COVID-19 pandemic.