Can a man and a woman live together without marriage?

 

Islam prohibits private seclusion between non-mahrams. Private seclusion is defined as being present in a place where a locked door prevents others from walking in and out of the room freely. Prophet Muhammad (peace and blessings be upon him) said: “No man is to seclude himself with a woman without her mahram being present.”
A mahram is defined as a woman’s male relative to whom marriage is unlawful i.e. her father, uncle, brother, brother-in-law etc. When a woman is in seclusion with her mahram, this seclusion is not considered prohibited.
Based on this understanding, if a man and a woman live together in a place where no one else can freely enter, it is considered a prohibited seclusion; therefore, it is impermissible for a non-married couple to live together.
And God Almighty knows best.