Ann-Mari Katharine Thomassen (born 1964) is a Sámi politician and a schoolteacher.
A member of the Norwegian Sámi Association and the Sámi Parliamentary Council, she has served as a member of the Sámi Parliament of Norway from 2001 to 2005, from 2005 to 2009 and from 2013 to 2017.
Thomassen has been a strong supporter of the requirement for Sámi educators to be employed in Oslo's Sámi kindergarten.