Professional Engineers Ontario (PEO) is the licensing and regulating body for professional engineering in the province of Ontario. Established in 1922, PEO governs over 90,000 license and certificate holders, ensuring the protection of the public interest. Under the authority of the Professional Engineers Act, PEO sets high academic, experience, and professional practice standards for the engineering profession.

Only individuals licensed by PEO are permitted by law to undertake and assume responsibility for engineering work in Ontario. PEO's mission is to regulate and advance the practice of engineering to protect the public interest. They strive to be the trusted leader in professional self-regulation, upholding their core values of accountability, respect, integrity, professionalism, and teamwork.

PEO's activities include overseeing Council, creating committees, maintaining chapters and regional offices, conducting annual general meetings, and publishing the official Engineering Dimensions magazine. They also operate a government liaison program, a student membership program, and offer various resources and guidelines to support practicing engineers. Overall, PEO plays a vital role in ensuring the competence and ethical conduct of professional engineers in Ontario, safeguarding the public's trust in the field of engineering