The particle that has the same mass as a hydrogen atom is a proton.

Here's why:

* Hydrogen atom: A hydrogen atom consists of one proton and one electron. While the electron has a very small mass compared to the proton, it still contributes to the overall mass of the atom.

* Proton: A proton is a subatomic particle found in the nucleus of an atom. It carries a positive charge.

The mass of a proton is almost identical to the mass of a hydrogen atom because the electron's mass is so much smaller.