Is it permissible to kill a critically ill or suffering animal (euthanasia) to end its suffering?

Summary

The default ruling is that euthanasia of a sick animal is not permitted, as it counts as killing without a valid Shariah reason and is an injustice against a living creature. As long as the animal can be cared for and treated, it must be left alive. The view permitting euthanasia may be applied only to a dying or critically ill animal when the harm of leaving it alive is greater than the harm of euthanasia, with very high treatment costs being an additional consideration in such cases. The fatwa notes scholarly differences: the Hanafi and Maliki schools permit it in certain cases, while the Shafi'i and Hanbali schools prohibit it.

Written in our own words from the original fatwa — check the source before acting on it.