What type of triangle has three sides of equal length?

The type of triangle that has three sides of equal length is known as an equilateral triangle. In geometry, an equilateral triangle is defined not just by its equal side lengths but also by the fact that all three interior angles are equal, each measuring 60 degrees. This symmetry makes equilateral triangles a fundamental shape in various applications, from architecture to art.

Scalene triangles, on the other hand, have all sides of different lengths, which does not fit the definition in question. An obtuse triangle has one angle that is greater than 90 degrees, but this classification refers to the triangle's angles rather than its side lengths. An isosceles triangle has at least two sides that are of equal length, which again does not meet the criterion of having all three sides equal.

Thus, the defining characteristic of an equilateral triangle is its three equal sides, making it the correct choice in this scenario.