Is there free will?

Christianity teaches that God gave humans free will, since Objectivism is an atheist philosophy, is Objectivism against free will?

No, Objectivism is not "against free will," nor can it be rational to deny the faculty.

The determinist premise fails in multiple ways, including the fallacy of self-exclusion - anyone who makes a claim against free-will has no answer to the question, "aren't you compelled by circumstance to make that claim, regardless of its truth or falsity?"

If not, [w]here does Objectivism say free will comes from?

As a phlosophy. Objectivism makes no assertions on the scientific basis of free-will, beyond understanding that it exists, that it is is a natural faculty arising from Man's unique conceptual nature.

Ayn Rand uniquely understood the locus of free-will to be Man's choice, in any given instance, at any given moment, to think or not, to focus his awareness, or not.

(More information at the Ayn Rand Lexicon.)

It is telling that you assume that free will is a mystical fact. It is not uncommon to assume that free will is something existing outside of the causal framework: that there is this natural world, and beyond a supernatural world, in which exists our souls (with their free will). Under this framework, free will is something of "god's gift", something unpossessed by anything which just exists in the natural world.

Objectivism rejects the whole notion of a natural/supernatural divide, and characterises causality in a way opposed to the mystical view. In the mystical view, there is nothing essentially causing entities to act in a particular way. That a billiard ball acts in a certain way today is no guarantee, just by its being a billiard ball, that it will act that way tomorrow. Rather, it is God's will that it will be so, and it is but for the grace of God that things are as they are (or in more modern terms: the will of our collective consciousness and its arbitrary scientific explanations of reality). Everything is a matter of God's choice -- with the exception of our souls, to which he has given free reign (the theological problems of what we are free to do, if our material bodies are bound but our souls are free, I shall not get into).

By contrast, Objectivism recognises: (i) That A is A, that reality is as it is because it is reality; (ii) free will is an axiom

(i) is to state that reality requires no justification. Why are entities such as they are? Because they exist. To exist is to exist with a particular identity, and there is no justification for that fact -- to assume otherwise is to begin with consciousness as a primary, which is precisely what the mystical view above is doing.

As a corollary, it recognises that all causal acts, including that of free agents, are simply facts of reality. It is an observable (and axiomatic) fact that we have free will, and the fact of its existence is usually not what the mystic (of mind) rejects (if you want to ask from a determinist's perspective, or the "mystic of muscle", feel free to ask again).

(ii) To state that free will is an axiom is to state, more precisely than that it is a fact of reality, that it is an indisputable fact of all our thinking. It is impossible to proceed in any line of enquiry without first assuming that you are free to do so, that the logical chains you try to develop are a matter of your trying, and not something destined to happen. If you disagree that free will is axiomatic, you are free (pardon my pun) to do so, but you have to accept that any argument about the fact is pointless, and I am not to be blamed for disagreeing with you. You abdicate yourself from the entire realm of argument altogether, because you assume that no arguments are necessary: whatever thinks, one is going to think anyway. All talk is just the parroting of God's (or whomever's) pre-ordained whim.

If you would like to read more on the topic, I highly recommend Dr Peikoff's coverage of the issue in OPAR; for more specific details on the function and nature of free will, I recommend Dr Binswanger's article on 'Volition as cognitive self-regulation', at the top of the list here:

http://scholar.google.co.uk/scholar?hl=en&as_sdt=2000&q=binswanger+volition

Choice and intelligence go hand in hand.

An organism that can detect preferable circumstances, but cannot act accordingly would be a perversity. That does not mean animals have free will, because what choice they will make, such as to turn left or to turn right, is set by their nature, (and their education,) given what they perceive to be on their left at the moment, versus what's on their right.

The education of sub-human animals means exposing them to certain things--usually other animals--and situations so that he learns life-serving relations, such as the edibility of furry, moving things once they are caught and killed. It remains true, though, that such animals' choices remain under the control of their physiological needs and conditioned appetites, as triggered by a set of perceptual stimuli, meaning their immediate environment.

Man's intelligence exceeds that of all other animals so much that he creates a cognitive tool, the linguistic system of symbols, that makes his own cognitive products manipulable in a new way. It is in connection with this tool for fixing and manipulating his concepts that a new degree of freedom comes to exist.

Whereas the sensory-perceptual level of cognition is driven by experience, man's linguistic level of cognition allows him to think of and consider other than what is perceptually given, or merely a learned associate to what is perceptually given. Thought is free of the perceptually given, both in its content and in its occurrence. Therein lies a kind of independence no other animal or creature enjoys. This independence separates the individual from all other individuals, and from the circumstances of his immediate place in time and space. That independence is the freedom of free will.

As compared to a religious theory of volition, the Objectivist theory is fact-based, and has explanatory power. Also, one of religion's concerns is to distinguish man from the lower animals in a categorical way, and the Objectivist theory of volition does that.

The other three answers are more than sufficient for the question. However, it might be of worth to point out that Christianity posits numerous "facts" concerning God and man. Perhaps the most insidious is that of original sin. If man was created with free will, how can one also state that man is innately sinful? At the foundation of Christian thought is Paul's idea of Faith. All must be accepted by faith and all is possible with faith. One apparently does not need to strive to do right since faith is all that is needed. I realize that I am simplifying a complex concept and theology. however, I have come to a point at which i accept nothing based on faith.

It is because we are free to act independent of some spiritual all powerful supernormal power that we as men are capable of doing great things (or, for those so inclined, doing terribly things). We do not need God to enable free will, we simply need to be human.