90 (ninety) is the natural number preceded by 89 and followed by 91.

• Interstate 90 is a freeway that runs from Washington to Massachusetts.
• The latitude of the North Pole and the South Pole are 90 degrees.
• Major League baseball bases are 90 feet (27 m) away in distance.
• The car number most associated with former NASCAR team owner Junie Donlavey.
• The number of minutes in a football (soccer) match.
• Ninety is the atomic number of thorium, an actinide. As an atomic weight, 90 identifies an isotope of strontium, a by-product of nuclear reactions including fallout. It contaminates milk.
• 90 is the number of degrees in a right angle.