Is a toenail fungus contagious?

Yes: Fungi are living microorganisms, so toenail fungus can spread from one toe to another. However, it's hard to predict how likely it is for the fungus to spread to another toe.

Can be: A nail fungus can spread from nail to nail, nail to skin. It is possible to pass it on to others.

Yes: Toenail fungus is an infection. Similar to a bacterial infection except the growth rate is much slower. Although fungus is not as contagious as some bacterial infections, under the right circumstances and on the right host the infection can be contagious.

Yes, but...: only if another nail or skin, yours or someone else's, is susceptible. You can spread mushroom spores all over the neighborhood, but only certain lawns in certain spots will sprout mushrooms. It's the same thing on the human body. If another nail on you or someone you're close with is susceptible, then there is a risk of transmission. If not, they're safe.