Killing ants is generally prohibited in Islam. This is based on a hadith narrated by Ibn Abbas (may Allah be pleased with him), where the Prophet Muhammad (peace and blessings be upon him) forbade the killing of four creatures: ants, bees, hoopoes, and sparrows. This hadith is recorded by Ahmad and Abu Dawood.

However, it is permissible to kill ants that cause harm to humans or their belongings, such as the white ants known as termites. Some scholars have interpreted the prohibition to apply specifically to a certain type of ant, like the large red ant, which generally does not cause harm.

For more details, you can refer to the fatwa on IslamWeb.

And Allah knows best.