This is a list of topics related to pi (π), the fundamental mathematical constant.

• 2π theorem
• Approximations of π
• Arithmetic–geometric mean
• Bailey–Borwein–Plouffe formula
• Basel problem
• Borwein's algorithm
• Buffon's needle
• Cadaeic Cadenza
• Chronology of computation of π
• Circle
• Euler's identity
• Six nines in pi
• Gauss–Legendre algorithm
• Gaussian function
• History of π
• A History of Pi (book)
• Indiana Pi Bill
• Leibniz formula for pi
• Lindemann–Weierstrass theorem (Proof that π is transcendental)
• List of circle topics
• List of formulae involving π
• Liu Hui's π algorithm
• Mathematical constant (sorted by continued fraction representation)
• Mathematical constants and functions
• Method of exhaustion
• Milü
• Pi
• Pi (art project)
• Pi (letter)
• Pi Day
• PiFast
• PiHex
• Pi in the Sky
• Pilish
• Pimania (computer game)
• Piphilology
• Proof that π is irrational
• Proof that 22/7 exceeds π
• Proof of Wallis product
• Rabbi Nehemiah
• Radian
• Ramanujan–Sato series
• Rhind Mathematical Papyrus
• Salamin–Brent algorithm
• Software for calculating π
• Squaring the circle
• Turn (geometry)
• Viète's formula