No. Ahl al-Sunnah hold that whoever commits a major sin short of shirk — fornication, theft, drinking, and the like — remains a Muslim whose iman is deficient: a believer by his faith, a sinner (fasiq) by his sin, and under Allah's will in the Hereafter, punished if He wills or forgiven if He wills. This is against the Khawarij, who declared such a person an apostate, and the Mu'tazilah, who invented a "station between two stations" (al-manzilah bayna al-manzilatayn). Allah says He does not forgive shirk "but He forgives what is less than that for whom He wills" (4:48, and again 4:116), and He continued to call two warring parties "believers" (49:9). Sins that are themselves disbelief — such as mocking the religion or denying what is necessarily known of it — are a separate matter, and ruling that a specific named individual has left Islam belongs to qualified scholars and courts, not to laymen.
Q&A · Belief
Does committing a major sin make a Muslim a disbeliever?
Evidence — the daleel
Quran 4:48Quran 4:116Quran 49:9Sahih al-Bukhari and Sahih Muslim — hadith of Abu Dharr: Jibril told the Prophet ﷺ that whoever of his ummah dies not associating anything with Allah will enter Paradise, 'even if he committed fornication and even if he stole'
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.