The Winsor School is a 5–12 private, college-preparatory day school for girls in Boston, Massachusetts, United States. It was established in 1886. It competes in the Eastern Independent League and is featured on the Boston Women's Heritage Trail. In late 2007, The Wall Street Journal identified it as one of the world's top 50 schools for its success in preparing students to enter top American universities. In April 2010, it was named one of the top 10 prep schools in America by Forbes. In 2018, Niche.com ranked it as the best all-girls school in the United States, the 15th best private school in the country, and the 2nd best high school in the Boston area.