Short stories containing religion.

Isaac Asimov, “Reason”
This robot creates a new religion.

Isaac Asimov, “The Mayors”
A scientific culture can tame a more primitive one, claiming science is actually religion.

David Barr Kirtley, “Cats in Voctory”
The memories of the past have turned into a religion.

James Blish, “A Case of Conscience”
Is this planet paradise?

Anthony Boucher, “The Quest for Saint Aquin”
A priest is looking for the body of a dead saint. Meanwhile a robot ass asks him about his faith.

Ray Bradbury, “The Fire Ballons”
MIssionaries come to Mars to convert the local people, if it’s possible. Maybe Christ needs to look like a blue sphere here.

Jonathan Brand, “Encounter with a Hick”
My father is in a company where they create worlds, and he created Earth in 6 days.

John Brunner, “Judas”
An allegory about Judas.

Ted Chiang, “Hell Is the Absence of God”
Christian. Belief isn’t necessary, as angels etc are clearly visible. However love is necessary, if you want to go to heaven.

Arthur C. Clarke, “The Nine Billion Names of God”
This religion believes, that the world will end when all the names of God have been written down.

Arthur C. Clarke, “The Star”
The supernova of this star has religious significance to us.

Greg Egan, “Oceanic”
This planet was colonized thousands of years ago. Now the story of that colonization only survives as religion. The story also illustrates how religion and science are 2 different ways of thinking.

Costi Gurgu, “Angels and Moths”
An encounter with an alien race suddenly requires “a man without faith”.

Harry Harrison, “The Streets of Ashkelon”
Teaching aliens Christianity.

Robert A. Heinlein, “If This Goes On…”
USA is super Christian, and a pious guard is shocked to learn the truth about the Prophet and the virgins.

Damon Knight, “Shall the Dust Praise Thee?”
“God arrives on Earth, ready to inflict the Day of Wrath on mankind, but finds that all life has already disappeared.”

George R.R. Martin, “Song for Lya”
Is a local religion an advanced group mind, or just a complicated way to commit suicide?

George R.R. Martin, “The Way of Cross and Dragon”
A local version of Christianity has a Saint Judas and dragons.

James Morrow, “Auspicious Eggs”
Births are few, far between and declared holy by the Catholic church. Priests help in this endeavour by drowning children, who will never become parents anyway. Do you know any more?

Lester del Rey, “Evensong”
“It details the capture of a being, identified at the end of the story as God, by Man, which has usurped God’s power.”

Mercurio D. Rivera, “Missionaries”
Sincere faith finally attracts an alien.

Norman Spinrad, “Deus X”
Uploaded people and artificial intelligences are common. The Catholic church has to decide whether these entities have souls.

H.G. Wells, “The Lord of the Dynamos”
I tell you, this piece of machinery is God.