If humans had spaceships capable of traveling interstellar distances, the closest potentially habitable exoplanet to Earth is Proxima Centauri b. Proxima Centauri b is an exoplanet orbiting the star Proxima Centauri, which is part of the closest star system to our Solar System, known as the Alpha Centauri system.
Proxima Centauri b is located approximately 4.24 light-years away from Earth. It was discovered in 2016 and is considered to be in the habitable zone of its star, meaning it orbits at a distance where liquid water could potentially exist on its surface. However, there are still many uncertainties about the actual conditions on Proxima Centauri b and whether it could support life as we know it.
It's important to note that interstellar travel is currently beyond our technological capabilities. The distances between stars are vast, and even with hypothetical advanced spaceships, travel times would be extremely long. Therefore, while Proxima Centauri b is the closest potentially habitable exoplanet we know of, it remains a subject of scientific study and speculation rather than a feasible destination for human colonization with our current technology.