Founded by the Teaching Profession Act of 1944, the Ontario Teachers' Federation (OTF) is the professional organization representing teachers in Ontario. It is made up of four affiliated groups, sometimes referred to as “professional associations” or “teacher unions”:

L'Association des enseignantes et des enseignants franco-ontariens (AEFO)
AEFO represents all teachers who work in the French language (also known as “francophone”) publicly funded schools in Ontario.

The Elementary Teachers' Federation of Ontario (ETFO)
ETFO represents all teachers who work in the public elementary English language schools in Ontario.

The Ontario English Catholic Teachers' Association (OECTA)
OECTA represents all teachers who work in the Catholic English language schools in Ontario.

The Ontario Secondary School Teachers' Federation (OSSTF)
OSSTF represents all teachers who work in the public secondary English language schools in Ontario.

All teachers who work in Ontario's publicly-funded school system belong to one of these four organizations as well as OTF. OTF's responsibilities include promoting and advancing the cause of public education, raising the status of the teaching profession and promoting and advancing the interests of teachers. OTF also represents teachers and all other members of the Teachers' Pension Plan in the administration of the Plan and management of the pension fund, and acts as the link between teachers and the Ontario Ministry of Education. OTF's affiliates are responsible for negotiating teachers' salaries and benefits, protecting teachers' working rights and ensuring that all demands on teachers are made fairly.