jamie17

The short answer: No, weightlifting will not stunt your muscle growth, or any other kind of growth, for that matter. Be advised, though, that if you are still very young, and your body has not yet kicked your testosterone production into high gear, that wieghtlifting will not result in the kind of muscle gains you are expecting.

The long answer: traditionally, weightlifting has been discouraged in guys younger than, say, 15 or 16 because the thought was that their bodies were still very actively and rapidly growing, and because of that their bones and muscles, and especially their connective tissues, were very susceptible to injury if very careful attention wasn't paid to correct weightlifting form, or if too much weight was used and too much stress placed on the joints. This is still true, of course --- correct form should always be used by everyone, regardless of age, and no one should ever try to do more weight than they can reasonably lift, otherwise injury can occur. If you were to severly injure yourself while your body is still growing, I suppose that could negatively impact your growth, and maybe that's where this idea of weightlifting stunting your growth comes from.

However, the most current line of thought about weightlifting and children/preadolescents/adolescents is that weightlifting can be safe --- if (big if) done properly and under supervision --- by even children as young as 9 or 10, and that there can still be health benefits to their bodies, even though they will not be able to develop larger muscles until their testosterone kicks in. The main benefits, other than larger muscles, are increases in coordination and muscle control, and strengthening of the connective tissues around the joints. A different program of weightlifting for children that young must be undertaken than one for someone older, and presumably, the weightlifting would be done as part of an overall fitness or sports-readiness program, as opposed to "just to look better", as many adults do.

Sorry to get on the soapbox, but since childhood obesity (and obesity in general) is such a growing problem here in the US, anything one can do to develop positive health habits is a good thing, and encouraging a workout routine, even in adolescents, is a step in the right direction.
So go ahead and lift weights --- just (please!) make sure you get someone to show you how to do it properly, go slow, don't try to do too much at once, and be careful.