A doomsday scenario is a story of how we might meet our horrible end as a species, or even how the Earth might be destroyed. These range from the mythical, to the silly, to the paranoid, to the scientific.
- Armageddon, as described in the Book of Revelation in the Bible.
- 2012 apocalypse
- Earth changes
- The Third ImpactNeon Genesis Evangelion
- The alien overlords finally tire of anally probing us and vape the planet.
- Intentional human extinction - see Voluntary Human Extinction Movement
- The Gays create an evil gay-turning robot that turns everyone GAY!
- The colors of the rainbow grow so pretty in the sky they grain into the faces of all the people going by
- Someone will divide by zero. Luckily most calculators have safeguards against this, and will display an error if you try it.
- The Vogons actually do destroy earth for a Galactic freeway
- Priests in some lost Himalayan country complete writing down the 10,000 names of God.
- The New World Order takes over, and finally tires of anally probing us and vapes the planet.
- A "Camp of the Saints" scenario, from the novel by Jean Raspail of the same name, in which civilization collapses due to hordes of illegal immigrants
- Peak oil
- All life is reduced to grey goo due to nanotechnology
- Global thermonuclear war
- Total existence failure, every atom in existence deletes itself (scientific progress goes "boink")
- Numerous "how the universe may end" scenarios speculated on in popular science and science woo circles
- A large asteroid surprises us and impacts the Earth, totally screwing up Archer Daniels Midland's monopoly on genetically modified soybeans.
- A black hole drops in on the Solar System
- The sun becomes a red giant (no need to hurry)
- Burst of magnetism from a solar flare kills Earth's magnetic field
- Quantum fluctuations in gravity suck the Earth into the Sun (unlikely)
- Gamma ray burst from two stars colliding (absurdly unlikely)
- Galaxies collide together. Our next impact is scheduled in about 280,000 years.
- A new virus/bacteria/parasite evolves and eliminates mankind (not exactly doomsday because life will go on)
- Mass insanity - every person in the world goes insane (halfway there)
- Ecosystem collapse, acid rain or some other environmental disaster destroys the biosphere
- Overpopulation - the sheer demand for resources launches a mass global war
- Evolution takes over, and humans become a new species. The human race would be "extinct", but our descendants would still be here.
 Planet Terry
- Runaway global warming on a Venus-like scale
- Yellowstone National park blows its top (the entire park lies on a supervolcano that has gone off several times in the past) <insert fart joke here>
- Magnetic field reversal (every 780,000 years. Caveat, there is nothing in the fossil record to indicate that any previous reversals have caused any problems)
- Tectonics - the entire Pacific Ocean slides under Asia, sucking the California coast along with it. The Hawaiiian hotspot burns through and creates a massive volcano in Siberia. Europe crashes into the east coast of North America. The Himalayas fall over due to being too tall, wrecking most of India. Antarctica breaks into five sections, and each section proceeds north to destroy another continent.