Sigma Chi (ΣΧ) is one of the largest and oldest all-male, college, Greek-letter social fraternities and a secret society. Sigma Chi was founded on June 28, 1855 at Miami University in Oxford, Ohio when members split from Delta Kappa Epsilon. Sigma Chi has seven founding members: Benjamin Piatt Runkle, Thomas Cowan Bell, William Lewis Lockwood, Isaac M. Jordan, Daniel William Cooper, Franklin Howard Scobey, and James Parks Caldwell. Sigma Chi is a part of the Miami Triad, along with Beta Theta Pi and Phi Delta Theta.

The fraternity's official colors are blue and old gold, and its badge is a white cross with emblems on each of its arms: crossed keys on the upper arm, an eagle's head on the right arm, seven gold stars and a pair of clasped hands on the lower arm, and a scroll on the left arm. In the center of the cross, on a black background, are the gold symbols for the Greek letters Sigma (Σ) and Chi (Χ). The left and right arms are connected to the upper arm by gold chains.

Sigma Chi's purpose is to promote the concepts of Friendship, Justice, and Learning; its mission statement is to develop values-based leaders committed to the betterment of character, campus and community. Sigma Chi's vision statement is "to become the preeminent collegiate leadership development organization—aligned, focused and living our core values".