No. Deism is not a religion, it’s a philosophy.
Consider Christianity. In order to become a Christian, interaction with someone else is necessary. The interaction may take the form of verbal conversation, or the reading of text written by someone else, or probably both.
It is not possible to become aware of the Christian doctrine without an external influence. A person who has never heard of Christianity could not sit alone on the top of a mountain and suddenly become a Christian.
Religions are memes. They are delusions passed from one person to another and require no original thought. Religions have set beliefs and rituals which must be learnt and practiced. Life today is considered to be a dress rehearsal for an afterlife. Adherence to the prescribed belief promises a blissful afterlife, whilst transgressions and disbelief threaten eternal punishment. Guilt, sin and self-condemnation are all essential components of religious doctrines.
Religions are ‘off-the-shelf’, ready-made belief systems. They are driven by fear but are proclaimed to be driven by virtue. Believing one is virtuous leads to conceit and unjustified self-importance.
Religions thrive on faith. If faith and reality contradict, faith is considered to be right, and reality is considered to be wrong. If necessary, claims of miracles are used to substantiate faith and override reason.
Faith is indestructible because it is non-falsifiable. Proving that a religious doctrine is false is made impossible by the clever manipulation of fictitious miracles.
Deism has none of the above. Indeed, our person sitting alone on top of the mountain has all he needs to be a Deist. There is no requirement for influences from other human beings. There are no scriptures, no preachers, no persuasions, no threats. Dogmatic beliefs and superstitions are not part of Deism. Deism truly comes from within, fuelled by an awareness of the natural world. There is merely the realization that there is an organizing force behind the universe in which we live. This realization is borne of common sense.
Deism has no chains. It carries no baggage. There are no compulsions or abstinences that must be obeyed. There are no tantalizing promises or tormenting fears. Deism has no rituals which are intended to influence the future. There are no prophets or miracles to explain the impossible.
There is simply a quiet acceptance of the obvious. Deism is a very personal awareness and has no need for faith or the group therapy of formal religions.
Most of all, no one else is necessary.