I have naturally straight teeth with a gap on my front tooth. What treatment would you recommend? (photos)

I think Invisalign would be the perfect treament option to close the space and improve your smile.  The treament would likely take a few months and then you could wear retainers at night to prevent future relapse. Good luck. 

Since it is only a single gap and your
teeth look fairly proportionate, I would rule out the option of veneering or
bonding this tooth because it would look quite disproportionate to the rest of
the mouth. A possible scenario would be to look at some sort of braces, orthodontics
or possibly Invisalign. I would not look at veneering the
teeth but rather try and move the teeth to close the gap. Obviously any orthodontics
or movement of the teeth will require retention, as these will move back.

I would need a little more information than just the photo that you provided, but there might be some relatively simple solutions to your problem.Providing there's enough space between the top and bottom teeth, you can use a service such as Simpli 5 to pull the top front teeth back just enough to close the space. This service is a type of clear braces, just like Invisalign, however it is much less expensive. In some cases, your dentist can create the space needed if it doesn't already exist.As far as

Your first option to look into is Invisalign. Perhaps the spaces can be closed after wearing Invisalign braces for 4-6 months. Have uour dentist evaluate why the space developed. How is your underlying bone support. How is your bite?

Hello there!  I can definitely see what you are talking about.  I too had gaps once.  And what I first used to close them was dental composite bonding. That is what I recommend for you too.  Most affordable.  Most comprehensive.  And easy.  So you want to whiten. The best product in my office is Zoom! Whitening.  The over-the-counter whitening product that might work for you (not as good as in office) is the Crest White Strips product. You could try that.  So whiten first.  Bond second.  Do a search for an "accredited cosmetic dentist" in your area.  That dentist has submitted 5 cosmetic dentistry cases and has been passed on all of them.  That gives you the most assurance that the bonding will be done right and will be invisible. Good Luck!