The most common element in the universe is hydrogen. It accounts for about 75% of the elemental mass of the universe, making it by far the most abundant element

. Hydrogen is the simplest element, consisting of just one proton and one electron, which explains its dominance since it was primarily formed during the Big Bang nucleosynthesis shortly after the universe began

. Following hydrogen, helium is the second most abundant element, comprising roughly 24-28% of the universe's elemental mass

. Together, hydrogen and helium make up over 98% of the known matter in the universe. The next most common elements, far less abundant than hydrogen and helium, include oxygen, carbon, neon, nitrogen, magnesium, silicon, iron, and sulfur

. Oxygen ranks third in abundance but is significantly less common than hydrogen. In summary, hydrogen is the overwhelmingly dominant element in the universe, followed by helium, with all other elements making up only a small fraction of cosmic matter