Polytheism, or shirk in Islam, is the act of associating partners with Allāh or attributing divine qualities to anyone or anything besides Him. This includes worshiping others alongside Allāh, seeking help from idols, saints, or false gods, or believing that anyone else shares in Allāh’s power, knowledge, or authority.
Polytheism is considered the gravest sin in Islam because it contradicts the core belief in Tawḥīd (the oneness of Allāh). Allāh strongly warns against shirk in the Qur’an:
“Indeed, Allāh does not forgive associating partners with Him, but He forgives anything else for whom He wills.”
— Surah An-Nisa (4:48)