The Old South Church (built 1872-1875), also called the New Old South Church, is a church in the Venetian Gothic style at 645 Boylston Street on Copley Square in Boston, Massachusetts. It is one of the most important examples of John Ruskin's influence on American architecture.

This United Church of Christ (Congregational) meeting house is home to one of the older religious communities in the United States, organized by dissenters from Boston's First Church in 1669, and from that time known as the Third Church in Boston. The Third Church's congregation met first in their Cedar Meeting House (1670), then the Old South Meeting House at the corner of Washington and Milk Streets in Boston. Members of the congregation have included Samuel Adams, William Dawes, Benjamin Franklin, Samuel Sewall, and Phillis Wheatley. In 1773, Samuel Adams gave the signals from the Old South Meeting House for the "war whoops" that started the Boston Tea Party.

Construction of the "New" Old South Church began in 1872 under Boston architect Charles Amos Cummings, who also designed the Isabella Stewart Gardner Museum. Exterior ornament is executed in Roxbury puddingstone, with striped arches, tracery, and ironwork. The interior is of plaster with Italian cherry woodwork. The screen of wooden arches behind the choir was adapted from the Doge's Palace in Venice. Stained glass windows are by Clayton and Bell of London in 15th century English style. The church's organ was built in 1921 by E. M. Skinner of Boston for the St. Paul, Minnesota Municipal Auditorium, and brought to the church in 1982 when that building was demolished. It has 183 ranks and 8,672 pipes ranging from 0.25 inches to 32 feet in length.

The church's interior was originally stencilled in 1875. In 1905, the congregation commissioned Louis Comfort Tiffany to renovate the interior, and he covered the stained glass windows with deep purple Tiffany glass and redecorated the walls in a gold and purple pattern. The walls were in turn painted a pale gray in the 1950s. An extensive renovation was performed in 1984 to restore the interior to something like its original decor.

Boston, Massachusetts | Buildings and structures in Massachusetts