Joseph James Marzilli, Jr. (born 8 May 1958 in Stoneham, Massachusetts) was a member of the Massachusetts Senate. Marzilli, a Democrat, was elected to the Senate in a special election in December 2007, representing the communities of Arlington, Billerica, Burlington, Lexington and Woburn partway through his ninth term in the Massachusetts House of Representatives, representing Arlington and West Medford. He was the Senate Chair of the Committee on Tourism, Arts and Cultural Development. He also served on the Committees on Children and Families, Mental Health and Substance Abuse and Veterans' Affairs. He resigned from the chamber on November 14, 2008.

Marzilli has twice led successful fights to increase the minimum wage, giving the state the highest minimum wage in the nation. For three years he has led the effort to increase the pay for the lowest paid human service workers, increasing the salary account to its highest level ever this year. He was given the "Self Sufficiency" award by the Massachusetts Association of Community Action Programs award in 2006 for his work on behalf of low wage workers.

Marzilli wrote the law that expanded the earned income tax credit benefiting low wage workers. He initiated the effort to provide tax relief to seniors living on fixed incomes who pay high property taxes, the state’s "circuit breaker" law. He also led the effort to restore the capital gains tax in Massachusetts.