The Greek mathematician Euclid is also known as the "Father of....what"?

Euclid (flourished c. 300 BCE, Alexandria, Egypt), sometimes called Euclid of Alexandria to distinguish him from Euclid of Megara, was a Greek mathematician, often referred to as the "founder of geometry" or the "father of geometry".

Of Euclid’s life nothing is known except what the Greek philosopher Proclus (c. 410–485 CE) reports in his “summary” of famous Greek mathematicians. According to him, Euclid taught at Alexandria in the time of Ptolemy I Soter, who reigned over Egypt from 323 to 285 BCE.

Euclid's 'Elements' is one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematics (especially geometry) from the time of its publication until the late 19th or early 20th century. In the 'Elements', Euclid deduced the theorems of what is now called Euclidean geometry from a small set of axioms.

Although many of the results in 'Elements' originated with earlier mathematicians, one of Euclid's accomplishments was to present them in a single, logically coherent framework, making it easy to use and easy to reference, including a system of rigorous mathematical proofs that remains the basis of mathematics 23 centuries later.

Euclid also wrote works on perspective, conic sections, spherical geometry, number theory, and mathematical rigour.