Thomas Stelzer (born June 19, 1955) is an Austrian diplomat, who served as the Dean and Executive Secretary of the International Anti-Corruption Academy (IACA) until July 2023, when he was suspended by the IACA board on suspicion of corruption.

Stelzer served in a variety of diplomatic and international positions in his early career.

He was Deputy Director of the Austrian Cultural Institute in New York, Special Assistant to the Executive Secretary of the CTBTO Preparatory Commission, and Minister-Counsellor at the Permanent Mission of Austria to the United Nations in New York.

[2] Stelzer has been serving since August 2001 as Permanent Representative of Austria to the United Nations (Vienna),[3] United Nations Industrial Development Organization (UNIDO), International Atomic Energy Agency (IAEA), and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Preparatory Commission.

Most recently, he served as a Vice-Chair of the Second Conference of States Parties of the United Nations Convention against Corruption.