Ontario Secondary School Teachers' Federation

Ontario Secondary School Teachers' Federation

Abbreviation	OSSTF
Formation	1919; 105 years ago (1919)
Type	Trade union
Headquarters	Toronto, Ontario, Canada
Location	Ontario, Canada
Membership	60,000
President	Karen Littlewood
Affiliations	Canadian Labour Congress Canadian Teachers' Federation Ontario Federation of Labour Ontario Teachers' Federation
Website	osstf.on.ca

The Ontario Secondary School Teachers' Federation (OSSTF; French: Fédération des enseignantes-enseignants des écoles secondaires de l'Ontario, FEESO) is a Canadian trade union which represents 60,000 members across Ontario.

Founded in 1919, its membership includes public high school teachers, occasional teachers, teaching assistants, psychoeducational consultants, social workers, child and youth counsellors, speech-language pathologists, continuing education teachers, early childhood educators, instructors, and support staff from several Ontario universities.