Congregation Agudath Shalom, also known as Agudas Sholom the Walnut Street Synagogue or the Walnut Street Shul, is an active, historic Orthodox Jewish synagogue at 145 Walnut Street in Chelsea, Massachusetts.

The congregation was founded in 1887. The present building was erected in 1909, one year after the great fire that destroyed a third of the buildings in the city. The architect was Harry Dustin Joll. The congregation’s previous building was destroyed in the great fire.

The Walnut Street Synagogue is the oldest surviving synagogue in Chelsea, a city that was one-third Jewish at the time the synagogue was built.

The synagogue possesses a remarkable series of wall and ceiling frescoes painted by Jewish immigrant artists. The magnificent carved Torah Ark was created by a noted Boston-area cabinetmaker who specialized in synagogue furniture, San Katz, in the 1920s. The synagogue was added to the National Register of Historic Places in 1993.