Unity Temple is a Unitarian Universalist church building that houses the Unity Temple Unitarian Universalist Congregation at 875 Lake Street in Oak Park, Illinois, United States. The structure, designed by the architect Frank Lloyd Wright in the Prairie style, is cited as an early example of modern architecture. The building consists of an auditorium to the north and a church house called Unity House to the south. The two sections, and an entrance pavilion between them, are made of reinforced concrete.

The congregation was formed as the Unity Church of Oak Park in 1871. It originally occupied a Gothic Revival building and went through several pastors in its first two decades. Rodney Johonnot, who became the senior pastor in 1892, began planning a replacement structure in the early 1900s. After the original church burned down in 1905, the board of trustees selected a site on Lake Street and hired Wright to design a new building, Unity Temple. Wright's plans were approved in 1906 after much debate, and construction began on May 15 of that year. After various delays, Unity House opened in September 1907, and the auditorium was finished in October 1908; the church was dedicated on September 26, 1909. Over the years, the temple attracted visitors from around the U.S. and the world. The church was restored in the 1960s, and it gradually underwent further upgrades from the 1970s to the 2000s. Unity Temple was completely refurbished from 2015 to 2017.

The temple is decorated with abstract motifs instead of overtly religious imagery. The facade is made of Portland cement, which has been washed away to expose the gravel underneath; there are recessed clerestory windows near the top. Unlike contemporary churches, Unity Temple was designed without a spire; instead, the roof consists of multiple flat, overhanging concrete slabs. The auditorium is shaped like a Greek cross, with stair towers at each corner. It has two levels of seating surrounding a central pulpit, in addition to clerestories and skylights. Unity House has skylights and two balconies.

Unity Temple has received extensive architectural commentary over the years, and it has been the subject of many media works, including books and museum exhibits. Its design is credited with having helped inspire multiple architects. Unity Temple is designated as a National Historic Landmark and is part of The 20th-Century Architecture of Frank Lloyd Wright, a World Heritage Site.

Eleven members of the Union Church—a liberal Protestant congregation in Oak Park, a village in the suburbs of Chicago, Illinois—met on January 25, 1871, to discuss the formation of a new congregation. E. W. Hoard hosted a meeting to raise money for a church building, collecting more than $5,000. Unity Church of Oak Park, a non-denominational church, was formed that March. The congregation acquired land at the southwest corner of Wisconsin Avenue (later Pleasant Street) and Marion Street, south of the Union Pacific West railroad line, from Milton C. Niles. The treasurer, Edwin O. Gale, provided $5,600, or nearly half of the $13,689 cost. It is unknown who designed the original church, which was built in the Gothic Revival style. The original church was a 40-by-80-foot (12 by 24 m) rectangle topped by a 125-foot (38 m) spire. Inside was a ground-level parish hall with an auditorium above it; a Chicago Tribune article from 1872 described the church as having a stone foundation and wood frame. Within the auditorium was a raised pulpit and rows of seats bisected by a central aisle.

Work on the new church began in early 1871, and the basement was finished later that year. A consecration ceremony was held on August 11, 1872. In its early years, the congregation was composed of Universalists and Unitarians. As such, the church went through several pastors in its first decade. In 1882, some of the congregation's Universalist members formed a sub-congregation affiliated with the Universalist Church of America; the congregation at large remained unaffiliated with any denomination. After going through six pastors in fifteen years, the church selected Augusta Jane Chapin as its pastor in 1886. During Chapin's tenure, Anna Jones Wright, the mother of the architect Frank Lloyd Wright, joined the congregation.

Chapin left the congregation in December 1891, and Rodney Johonnot became the senior pastor the next year. During Johonnot's first four years, the congregation grew to 225 members. A church organ was installed in 1897. The congregation had decided to build a new structure by March 1901, when members voted to establish a fund for the construction of a new temple. Johonnot felt that the existing building could not accommodate all of the congregation's activities. The congregation hired H. P. Harned to design a new structure on the existing site, south of the railroad tracks. By then, numerous churches were being built in Oak Park, and many of the newer churches were being built on Lake Street, north of the tracks. In December 1904, the board of trustees again asked the congregation for donations for a new temple. Following a meeting in May 1905, a committee was appointed to discuss plans for the new building.

The original Unity Church was destroyed on June 4, 1905, when a lightning strike started a blaze; firefighters were unable to extinguish the flames because of low water pressure. The fire caused about $20,000 in damage and destroyed everything except for the piano, chairs, paintings, dishes, and utensils. Within one week, the congregation had appointed four committees to oversee fundraising, site selection, design, and construction. In the meantime, the congregation temporarily met at Nakama Hall. The nearby First Baptist Church also hosted some of the congregation's events.