Thandi Ruth Modise (born 25 December 1959) is a South African politician who served as the Minister of Defence and Military Veterans from 2021 to 2024. She was previously the Premier of the North West from 2010 to 2014, Chairperson of the National Council of Provinces from 2014 to 2019, and Speaker of the National Assembly from 2019 to 2021.

Modise has been a member of the African National Congress (ANC) since the 1976 Soweto uprising, when she dropped out of high school to join uMkhonto we Sizwe (MK), the ANC's armed wing, in exile. In 1978 she returned to South Africa as a trained guerrilla operative for MK and from 1980 to 1988 she was imprisoned under the Terrorism Act for her anti-apartheid activism.

She was elected to the South African Parliament in South Africa's first democratic election in 1994. After ten years in the National Assembly, she served as the Speaker of the North West Provincial Legislature from 2004 to 2009 before becoming Premier in 2010. She next returned to the executive branch of government in August 2021, when President Cyril Ramaphosa appointed her to replace Nosiviwe Mapisa-Nqakula as Defence Minister.

Modise has also held various senior positions in the ANC, including as Deputy President of the ANC Women's League from 1993 to 2003 under Winnie Madikizela-Mandela and as Deputy Secretary-General of the ANC from 2007 to 2012 under Jacob Zuma. She was first elected to the ANC National Executive Committee in December 1994, and she was re-elected to another five-year term on the committee in December 2022.

Modise was born on 25 December 1959 in Huhudi, a township near Vryburg in what is now the North West province (then the northern part of the Cape province). Her father, Frans Modise, was a railway worker (a stoker) and a member of the African National Congress (ANC), which was banned by the apartheid government the year after Modise's birth. She was the youngest of six children.

Modise was educated at Barolong High School until she dropped out in July 1976 during the Soweto uprising. The student protests were given particular fervor in Huhudi because of the imminent threat that the township would be incorporated into the so-called independent homeland of Bophuthatswana. Later in July, Modise, with some former classmates, fled to Botswana, crossing the border by foot, and joined the ANC in exile.

Modise received preliminary political education in Tanzania and then received military training at various Umkhonto we Sizwe (MK) camps in Angola and later in Maputo, Mozambique, becoming one of the few women in MK's famous "June 16" detachment. After her training she worked in MK camps as a political commissar, a section commissar, and ultimately a commander. She also sang soprano in a recreational MK choir.

In January 1978, shortly after her 19th birthday, Modise used a false passport to cross the Swazi border into South Africa, where she worked underground as an MK operative. She had received topographical training and her primary task was reconnaissance of potential targets for sabotage and other guerrilla attacks. She was based variously in Johannesburg, in Diepkloof, Soweto, and in Eldorado Park, and she occasionally crossed back into Swaziland to report back to the MK regional command stationed there. Over the course of two days in March 1978, she planted homemade incendiary devices, concealed in matchboxes, inside two OK Bazaars and Edgars stores in Johannesburg.