Mardi Gras arrives with rainbow flag

A rainbow flag will be raised in Sydney to kick off Mardi Gras festivities in the lead up to the annual parade.

Sydney's Gay and Lesbian Mardi Gras festival will officially kick off when a rainbow flag is raised over Town Hall.

The flag-raising ceremony will launch the festivities on Friday evening as 200 rainbow banners are scattered throughout the CBD in the lead up to the parade next month.

"These flags are a powerful symbol of our commitment to equality, social justice and diversity," Sydney Lord Mayor Clover Moore said in a statement.