What is the constellation closest to the earth?

You can't simply say which constellation is closest to the earth.

The projection of the stars on the celestial sphere is divided into constellations through human imagination.

So it is possible that some stars in the same constellation are close to the earth, while others are far away from the earth.

The closest star to the earth is the sun, then proxima centauri, and proxima centauri is the companion star of Alpha Centauri (the main star), about 4 light years away from the earth.