Guarini is a surname. Notable people with the surname include:
Giovanni Battista Guarini (1538–1612), Italian poet and diplomat
Anna Guarini, Contessa Trotti, (1563–1598), Italian virtuoso singer of the late Renaissance
Guarino Guarini (1624–1683), Italian architect and Theatine priest
Justin Guarini (born 1978), American singer who rose to fame on the television show American Idol