No. You cannot buy a life insurance policy on someone you don't know.

In order to purchase life insurance on another person you need an Insurable Interest in that person, and you would need their consent - permission to get the insurance.

Usually, the insurance company would require the signature on the application of the person you wish to insure.

That person would need to sign the application for life insurance coverage, which would verify that the person is aware of the life insurance coverage.

To learn more, read this article, "Can You Get Life Insurance on Someone You Don't Know?"