William Haloupek says
The nearest known star is Proxima Centauri, which is 4,234 light years (40 trillion kilometers) away. It's a red dwarf star, and there is some controversy whether it is in orbit around the second and third nearest stars, Alpha and Beta Centauri, or whether it is just passing through. If it is in orbit, the period will be at least half a million years.
Red dwarfs are very hard to see, even with infrared telescopes, and none of them can be seen from Earth, with the naked eye. It is still possible, though unlikely, that there are other red dwarf stars even closer, waiting to be discovered.