Author: Adam Glesser Title: Sparse Fusion Systems Abstract: We define sparse saturated fusion systems and show that, for odd primes, sparse systems are constrained. This simplifies the proof of the Glauberman-Thompson p-nilpotency theorem for fusion systems and a later related theorem of Stellmacher. We then define a more restrictive class of saturated fusion systems, called extremely sparse, that are constrained for all primes. Status: Submitting to Isle of Skye conference proceedings