A helion (symbol h) is the nucleus of a helium atom, a doubly positively charged cation. The term helion is a portmanteau of helium and ion, and in practice refers specifically to the nucleus of the helium-3 isotope, consisting of two protons and one neutron. The nucleus of the other stable isotope of helium, helium-4, consisting of two protons and two neutrons, is called an alpha particle or an alpha for short.
This particle is the daughter product in the beta-minus decay of tritium, an isotope of hydrogen:
CODATA reports the mass of a helion particle as  = 
Helions are intermediate products in the proton–proton chain reaction in stellar fusion.
An antihelion is the antiparticle of a helion, consisting of two antiprotons and an antineutron.