Todd Michael Muller (/ˈmʌlər/; born 23 December 1968) is a New Zealand former politician who served as the Leader of the New Zealand National Party and the Leader of the Opposition from 22 May to 14 July 2020. Muller entered Parliament at the 2014 general election. He was elected as the MP for the Bay of Plenty electorate, which held until his retirement at the 2023 general election. In his second term, Muller became the leader of the National Party after successfully challenging then-leader Simon Bridges. However, his mental health suffered, including suffering panic attacks, and he resigned the leadership after 53 days.

Muller was born in Te Aroha on 23 December 1968, where his grandfather Henry Skidmore was mayor, and was raised in Te Puna, where his parents started a kiwifruit orchard. He attended St Joseph's primary school in Te Puna, Te Puna primary school and Tauranga Boys' College. Muller recollected in 2020 that for two years he was the only Pākehā boy at St Joseph's. He became interested in politics at a young age, once authoring a story in which he served thirteen consecutive terms as President of the United States.

He studied English, history and politics at the University of Waikato and graduated with a master's degree.

Muller joined the New Zealand National Party in 1989. From 1994 to 1997 he worked as executive assistant to Jim Bolger during his second term as prime minister.

Muller started his corporate career working for kiwifruit company Zespri as industry relations manager from 2001 to 2003. He lists his CV as including the role of general manager corporate and grower services from 2003 to 2006, followed by a move to the position of chief executive at Apata Ltd in January 2006. Apata, a Bay of Plenty company specialising in post-harvest operations, was founded by his father and others in 1983. Muller was approached to contest the Tauranga electorate for the National Party in 2008, which was being vacated by incumbent MP Bob Clarkson. Muller declined, preferring to progress his commercial career, and the seat was won by Muller's eventual predecessor as National Party leader, Simon Bridges.

Muller started work at dairy company Fonterra as manager of local government and regional relations from February 2011 to May 2012. He then became group director of co-operative affairs in May 2012. He was part of the leadership group that responded to the 2013 Fonterra botulism scare and product recall.

Muller held various directorships in the agribusiness sector. From June 2011 to June 2014 he served as a director of Plant and Food Research, a New Zealand Crown Research Institute that undertakes research and development to add value to fruit, vegetable, crop and food products. From August 2012 until June 2014, Muller served as a director of the Sustainable Business Council. He served as a co-opted Waikato University councillor from October 2007 to June 2014.

Muller left Fonterra and his directorships in June 2014 to campaign for the 2014 general election after being selected as the National Party candidate for the Bay of Plenty electorate.