Montseng Margaret Tsiu is a South African politician, trade unionist and nurse who served as the Member of the Executive Council (MEC) for Health in the Free State provincial government from May 2018 until March 2023.

Tsiu is the former provincial chairperson of the National Education, Health and Allied Workers' Union and the former director of nursing in the Free State government.

She became an ANC member of the Free State Legislature on 23 April 2018, filling the vacancy created by the resignation of William Bulwane who had been sworn in two weeks earlier.

In May 2020, Tsiu and Dr David Motau welcomed 17 Cuban doctors to the Free State to assist the province in dealing with the pandemic.

[10] On 14 March 2023, newly elected Free State premier Mxolisi Dukwana named his executive council following Ntombela's resignation in February; former MEC Mathabo Leeto was appointed to succeed Tsiu.