The right to my own life.

I own myself.

The most fundamental right is definitely the right to life, in Objectivism. All other rights are derivatives of the right to life.

The right to life implies the right to be left alone;
it does not mean that your neighbors have to pro-
vide you with necessities, but that they should not
interfere with your providing yourself with necessit-
ies.

The right to life and not having it extinguished because of the demands of the tribe, majority or et al. This right can be recognized as being in force when other rights are not infringed upon such as; the right to property and its use or function, the right not to be enslaved to fight wars, the right to use property without getting permission from 'authority', or pay tax for having used it. Property cannot be bonded without permission, indebtedness caused by the vote of others is insignificant to the owners right to say no. The right to leave may be used in many ways, the right to leave the Affordable Care Act because I want to, no reason need be given, it does not have to be justified to the group in order for me to exercise my liberty. The right to say no is probably the most important signal that people are not slaves. If you cannot say no until you have permission to say no from the authorities you are not free. If the product of your labor can be taken from you and given to others simply because you did produce you are a slave. We are not chattel slaves in America but we are slaves of the state and consequently are slaves of any who demand our compliance, productivity and the right to tax anything we own simply because we own it.

"The right to life is the source of all rights - and the right to property is their only implementation. Without property rights no other rights are possible. Since man has to sustain his life by his own effort, the man who has no right to the product of his effort has no means to sustain his life. The man who produces while others dispose of his product is a slave." AR from "Man's Rights" VOS. Can't have one without the other.

It is the right to say NO.
Without that, no other right is possible, including the right to leave.

I would think that the most basic right, is the right to Life followed Extremely closely to the right of Self Defense. For without the right of Self Defense there is no way to protect the right of Life.

I`ll get back to you - gotta go....

The "right" to leave assumes freedom of action and therefore the right to life. Thoreau said "NO" to paying a poll tax but he still went to jail. While there he had the freedom to think and write but without the freedom to "leave" (i.e. right to life) we never would have had Civil Disobedience.

absolutely

Freedom "from" is subsumed into freedom "of." Therefore, freedom from association is a derivative of freedom of association. The European collectivists were shocked at Brexit, weren't they?

I think there are several "fundamental" rights, and leaving is one of them.

https://objectivismforintellectuals.w...

The three axioms are the most fundamental to Objectivism.