Euclid lived in Alexandria in Egypt, in about 300 BC. He is the most famous ancient Greek mathematician. Nothing much is known about Euclid's life because he lived so long ago. It is know however that he founded a school in Alexandria, where he taught maths. He is famous because of a book he wrote about maths called The Elements of Geometry. The Elements of Geometry was used as the basic maths textbook in schools all over the world for 2000 years. It has been translated into many different languages. Before printing was invented it was first copied by many different people like Abelard of Bath and Gerard of Cremona in the Middle Ages. More than one thousand different versions of it have been brought out since the first printed versions 1482. The first person to translate it into English from its original Greek was Sir Henry Billingsley. The Elements of Geometry is so good that some people say that Euclid couldn't have written it himself and that it was written by a team of mathematicians instead.

Euclid's Elements contains lots of mathematical theories or 'theorems', starting at the most basic. It is divided into 13 books. Books one to six deal with plane geometry, i.e. geometry on a flat surface. Books eleven to thirteen deal with three-dimensional geometry. Euclid's very first theorem is very basic indeed and states that it is possible to draw a straight line between any two points. Euclid then went on to talk about the properties of triangles, parallels, parallelograms, rectangles and squares.

One well known story about Euclid is that when one of his pupils asked him 'What do I get out of learning geometry?' Euclid told his slave to give the pupil three pence so that he would 'gain something from what he learnt'!