The Mother of Us All is a two-act opera composed by Virgil Thomson to a libretto by Gertrude Stein. Thomson and Stein met in 1945 to begin the writing process, almost twenty years after their first collaborative project, the opera Four Saints in Three Acts. Stein wrote the libretto in the winter of 1945–46 before sending it to Thomson in March. After Stein's death in July, Thomson began working on the score, which he finished within just a few months. The opera centers around Susan B. Anthony, one of the major figures in the fight for women's suffrage in the United States, with a supporting cast of characters both fictional and based on other historical figures. Thomson famously described the work as a "pageant".

According to experts, Gertrude Stein's exploration of rhythm and repetition within her writing lent itself to a musical setting. Both her libretto and Thomson's orchestration were highly idiomatic, matching patriotic dialogue with "hymns, marches, patriotic airs, and parlor songs" in order to emulate the atmosphere of America's 19th century political scene. Scholars claim that these folk influences are what mark Thomson's score as acutely American. Contrary to Four Saints in Three Acts, the focus of The Mother of Us All was on distinctly characterizing each political player—Thomson gave each a particular musical identity through his melody and orchestration. "Some characters are associated with specific instruments, most noticeably Susan B., who is associated with trumpets and strings, but also Angel Moore with the harp, and Daniel Webster with horns." Susan's trumpet melodies are "possibly meant to convey her militant dedication to her cause," and the character of Angel Moore, being a literal angel, is accompanied with the instrument most often associate with heaven. Though he still worked within a traditional tonal framework, Thomson was highly influenced by serialism and other contemporary musical ideas. The opera's duration is around 103 minutes.

The work is scored for one flute, one oboe, two clarinets, one bassoon, two French horns, two trumpets, one trombone, two percussionists, harp, celesta, piano, and strings. The cast consists of two sopranos, one alto, two tenors, one baritone, and one bass, with twenty five singers and six additional silent actors. When the piece was originally commissioned in 1945, Thomson was asked to orchestrate the piece for less than twenty players, since World War II made it difficult to recruit musicians. His chamber ensemble and solo piano reductions of the opera's orchestration are frequently performed.

The opera premiered on 7 May 1947 at Columbia University's Brander Matthews Hall with soprano Dorothy Dow as Susan B. Anthony. Soprano Shirlee Emmons was awarded an Obie Award for her portrayal of Susan B. Anthony in the 1956 Off-Broadway production. The opera was mounted at Carnegie Hall by the American Opera Society in 1964 with Johanna Meier as Susan B. Anthony, Betty Allen as Anne, Thomas Paul as Daniel Webster, and Enrico Di Giuseppe as John Quincy Adams. The Santa Fe Opera mounted the work in 1976 and released a recording of the work the following year on the New World Records label. The European premiere took place in Kensington Town Hall in London on 26 June 1979. The New York City Opera staged a production in 2000 with Lauren Flanigan as Susan B. Anthony. In 2003, San Francisco Opera opened its 80th anniversary season with a new production of The Mother of Us All, Luana DeVol assuming the role of Susan B. Anthony for the first time.

Stein's text for The Mother of Us All does not describe details of staging. Therefore, Thomson's partner Maurice Grosser devised a scenario to facilitate staging the opera. Though Grosser stated that other scenarios were equally possible, his scenario is published in the printed score; this synopsis is based on it.

Scene 1. Susan B. Anthony and her devoted companion Anne are shown at home. Anne is knitting; Susan B. is pasting clippings into a scrapbook. Gertrude S. and Virgil T. also appear as narrators.

Scene 2. A political meeting takes place, at which Webster, Johnson, Adams, Grant, Comstock, and Stevens are all present. Jo the Loiterer and Chris the Citizen also appear, mocking the politicians' solemnity. Susan B. introduces herself to the assembly, and she and Daniel Webster debate.

Scene 3. A public square in front of Susan B. Anthony's house. Thaddeus Stevens argues with Andrew Johnson; there is a flowery love scene between John Adams and Constance Fletcher. Jenny Reefer begins waltzing with Herman Atlan, and everyone joins in the dance.