The four horsemen of the Apocalypse are described in the Bible,  Revelation chapter 6, verses 1-8.

The four horsemen are symbolic descriptions of different events which will take place in the end times. These are just the first four of even worse judgements to come later in chapters.

Four Horsemen of Apocalypse, by Viktor Vasnetsov. Painted in 1887.

The White Horse  — Conquest

“I saw, and look! a white horse, and the one seated on it had a bow; and a crown was given him, and he went out conquering and to complete his conquest.”—Revelation 6:2.

The Red Horse — War

“Another came out, a fiery-colored horse, and it was granted to the one seated on it to take peace away from the earth so that they should slaughter one another, and he was given a great sword.”—Revelation 6:4.

The Black Horse — Famine

“I saw, and look! a black horse, and the one seated on it had a pair of scales in his hand. I heard what sounded like a voice in the midst of the four living creatures say: ‘A quart of wheat for a denarius and three quarts of barley for a denarius; and do not harm the olive oil and the wine.’”—Revelation 6:5, 6.

The Pale Horse — Death

“I saw, and look! a pale horse, and the one seated on it had the name Death. And the Grave was closely following him. And authority was given them over the fourth part of the earth, to kill with a long sword and with food shortage and with deadly plague and by the wild beasts of the earth.”—Revelation 6:8.

https://publicdomainreview.org/collections/the-four-horsemen-of-the-apocalypse/