Definition
Yes, in the sense that anyone with a recorded birth date has one waiting to be added up.
The interesting exception isn't a person — it's a birth date nobody can pin down, which turns out to be more common in history than you'd expect.
Quick answer
Yes. As long as your birth date is known, it can be reduced to a life path number using a standard numerology method. The only real gap is for people whose exact birth date was never recorded — historically not a rare situation.
This confirms that the calculation applies universally. It doesn't confirm that the resulting number carries the meanings tradition assigns to it.
Overview
Arithmetic can be checked
The life path calculation doesn't care who you are, where you were born, or what else is true about your life — it only needs three things: a day, a month, and a year. That makes it about as universal a numerology figure as exists.
Where things get genuinely uncertain isn't the person, it's the record. Throughout history, exact birth dates have been lost, approximated, or never written down at all, which is the one real gap in "everyone has one."
Historical figures, adoptees without birth records, and refugees issued estimated dates may only have an approximate figure to calculate from.
A birth date recorded in a non-Gregorian calendar needs converting first, and the conversion method itself can shift the final number.
A birth near midnight close to the international date line can genuinely be recorded on either of two calendar days depending on which zone's records are used.
Unlike some numerology figures that depend on a full legal name — and therefore run into spelling variants, name changes, and translation issues — the life path number only needs a date. That single dependency is exactly why it's treated as the most stable and most universally calculable number in the system.