Tree of Life – Or L'Simcha Congregation (Hebrew: עֵץ חַיִּים – אוֹר לְשִׂמְחָה[1]) is a Conservative Jewish synagogue in the Squirrel Hill neighborhood of Pittsburgh, Pennsylvania, in the United States.

In 1886, it affiliated with the Jewish Theological Seminary Association (JTS), at the time an Orthodox institution, but which developed the Conservative ideology in the early 1900s.

Tree of Life joined with JTS offshoot United Synagogue of America about 1916, formally connecting to the nascent Conservative movement.

[4] Tree of Life Congregation was formed in Pittsburgh, Pennsylvania, in 1864 as a breakaway group from Rodef Shalom, an Orthodox synagogue founded in 1854 which began adopting Reform practices following the visit of Rabbi Isaac Mayer Wise to the city.

[9] Beginning in the 1920s, Tree of Life shifted further toward left-wing Conservative Judaism under the direction of Rabbi Herman Hailperin, who led the congregation for 45 years.

[16] In 1959 the congregation broke ground on a 1,400-seat sanctuary fronted by "rows of swirling, modernistic stained-glass windows illustrating the story of creation, the acceptance of God's law, the 'life cycle' and 'how human-beings should care for the earth and one another".

[19] In April 2010, Dor Hadash, a Reconstructionist congregation, began renting space in the Tree of Life building.

[19] New Light, a Conservative congregation, left its home of 60 years in 2017 and carried its Torah scrolls in a procession to Tree of Life, where it also began renting space.

A gunman entered the building shouting antisemitic statements and opened fire, killing eleven and injuring six, including four responding police officers.

[24] The congregation elected its first spiritual leader, Rabbi Michael Fried, a graduate of the Jewish Theological Seminary, in 1898.