William Phillips, Jr. (April 10, 1750 in Boston, Massachusetts – May 26, 1827 in Boston) was a Boston merchant, politician and philanthropist.Phillips was the son of William Phillips, Sr., a merchant whom he joined in business and became wealthy. He was elected the tenth Lieutenant Governor of Massachusetts, serving from 1812 to 1823. He drafted the letter inviting New England Governors to send delegates to the Hartford Convention of 1815.