A triangle can have at most one right angle.
A right angle is an angle that measures exactly 90 degrees. According to the properties of triangles, the sum of all interior angles must equal 180 degrees. If a triangle had two right angles, that would total 180 degrees already, leaving no room for a third angle. Therefore, a triangle can only have one right angle while the other two angles must be acute (less than 90 degrees) or one could be obtuse (greater than 90 degrees), but together they will always complement the right angle to maintain the sum of 180 degrees.