Associate judges of the Ontario Superior Court of Justice preside over certain matters in civil cases which include motions, references, pre-trial conferences, and Construction Act trials. Associate judges also serve as Registrars in Bankruptcy under the Bankruptcy and Insolvency Act. An associate judge can also perform case management in certain family cases in accordance with rule 42 of the Family Law Rules.

The title of associate judge was created on September 1, 2021, to replace the former title of master and case management master. Associate judges are appointed under s. 86.1 of the Courts of Justice Act by the provincial Cabinet upon recommendation of the Attorney General of Ontario. Following their appointment, associate judges may hold office until they reach 65 years of age. Thereafter, their terms are reviewed on an annual basis, and they may be given additional one-year terms at the recommendation of the Chief Justice. An associate judge may not hold office once they reach 75 years of age.

Candidates for an appointment as an associate judge must have been a member of a Canadian provincial or territorial bar for a minimum of 10 years and have practiced law or have been a judge in Canada for at least 10 years.