"Denomination Blues" is a gospel blues song composed by Washington Phillips (1880–1954), and recorded by him (vocals and zither) in 1927. In 1972, Ry Cooder revived this almost-forgotten song on his album Into the Purple Valley.

In 1938, Sister Rosetta Tharpe (1915–73) recorded a gospel version of the song (vocals and guitar) under the title "That's All". She subsequently recorded several versions with orchestral accompaniment.

Phillips' song is in two parts, occupying both sides of a 78rpm single (it is over five minutes long, and could not have fitted on a single side because of technical limitations). In 1928, it sold just over 8,000 copies; a considerable number at a time when a typical single by Bessie Smith, "The Empress of the Blues", sold around 10,000.

The song is in strophic form: it consists of 17 verses sung to essentially the same music, all with a similar last line. In Part 1, Phillips gently mocks several Christian denominations for their particular obsessions (Primitive Baptists, Missionary Baptists, Amity Methodists, African Methodists, Holiness People, and ); and in Part 2, several types of people he felt were insincere in their beliefs (preachers who want your money, preachers who insist that a college education is needed to preach the gospel, and people who "jump from church to church"). Phillips is known to have attended several churches of different denominations, and the lyrics likely reflect his personal experience. His own faith was uncomplicated, as these extracts from the lyrics show:

I want to tell you, an actual fact,
Every man don't understand the Bible alike,
But that's all, I tell you that's all,
But you'd better have Jesus, I tell you that's all.

Well, denominations have no right to fight,
They ought to just treat each other right. That's all.
...
You're fightin' each other, and think you're doing well,
And the sinners on the outside are going to hell. And that's all.
...
It's right to stand together, it's wrong to stand apart,
'Cause none's going to heaven but the pure in heart. And that's all.

...
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