The Workplace Safety and Insurance Board (WSIB) is the workplace compensation board for provincially regulated workplaces in Ontario, Canada. As an agency of the Ontario government, the WSIB operates "at arm's length" from the Ministry of Labour, Training and Skills Development and is solely funded by employer premiums, administration fees, and investment revenue. The WSIB is one of the largest compensation boards in North America and is primarily responsible for administering and enforcing the Ontario Workplace Safety and Insurance Act (WSIA).

Over 100 years old, WSIB covers over five million people in more than 300,000 workplaces across Ontario and works to promote health and safety in the workplace with a goal of one day having zero work-related injuries or illnesses.

The Hon. Sir William Ralph Meredith, Chief Justice of Ontario, is the founding father of Workmen's Compensation in Ontario and by extension Canada.

In 1910, Ontario Premier Sir James Whitney [1905 - 1914] appointed Sir William Meredith to head the first Royal Commission into the "laws relating to the liability of employers to make compensation to their employees for injuries received in the course of their employment which are in force in other countries, and as to how far such laws are found to work satisfactorily".

In 1913 Sir William Meredith delivered his Final Report. The agreement between workers and employers creating the first workers compensation board in Canada was called the Historic Trade Off.

However due to pressure from employers the Final Report was shelved. Premier Whitney fell ill in 1914 and Acting Premier William John Hanna did introduce the Workmen's Compensation Act of Ontario becoming law on Jan. 1,1915.

The Historic Trade Off saw workers surrender their Right to the Courts in exchange for the 5 Meredith Principles and employers lost their "fault" defenses. 1. Non adversarial adjudication Sir William Meredith was loath to exchange one adversarial system, the courts, for another. Benefit of doubt to the injured worker, Sir William Meredith closed all loopholes that would impede an injured worker from collecting compensation for a workplace injury. No-fault, Sir William Meredith turned one of the fault defenses against employers, reasoning that if accidents were inherent in the work, then the accidents were inevitable and therefore no ones fault. 2. Compensation for a workplace injury expressed as a percentage of wage, for the life of the injury. Sir William Meredith gave his reasons for the duration being the life of injury in his Final Report. This is the Right workers exchanged the Right to the Courts for. 3. 100% employer funding were assessments collected were to be used exclusively for the benefit of injured workers. Sir William Meredith designed the system so that injured workers would not become a burden on relatives, friends, or the community. 4. Collective liability to ensure security of payment to the injured worker. An added bonus is that collective liability also was an edge against bankruptcy for employer. 5. Autonomous Board, with exclusive jurisdiction, doing what is just to the injured worker. The Provincial Governments entire role in workers compensation was to appoint honourable men to administer the Historic Trade Off.

WSIB differentiates between two types of employers, as set out in the Workplace Safety and Insurance Act (WSIA):