Matias Brain

{{Short description|Chilean triathlete (born 1974)}}

{{family name hatnote|Brain|Peña|lang=Spanish}}

Matias "Mati" Brain Peña (born January 15, 1974, in Santiago) is a Chilean triathlete. Nicknamed "Mati", Brain competed at the first Olympic triathlon at the 2000 Summer Olympics. He took forty-first place with a total time of 1:53:44.90.