The Headmasters' and Headmistresses' Conference (HMC) is an association of the headmasters or headmistresses of 275 independent schools (both boarding schools and day schools) in the United Kingdom, Crown dependencies and the Republic of Ireland. There are also International Members (mostly from the Commonwealth) and 30 Associate Members who are head teachers of state schools or other influential individuals in the world of education, who endorse and support the work of HMC.