TITLE: Has any error ever been found in Euclid's elements?
QUESTION [20 upvotes]: Has any error ever been found in Euclid's elements since its publication?
Or it is still perfect from the view point of modern mathematics.

REPLY [14 votes]: As pointed out by @Asaf, the very first theorem, Book I, Proposition 1, on the construction of an equilateral triangle, assumes two circles intersect but there is no axiom to ensure that.
The book Geometry: Euclid and Beyond by Hartshorne discusses this in section 11.