A person who shares the same religion or faith with another person.
From Latin cor- (with, together) and religionist (a person devoted to a religion). Emerged in English in the 17th-18th centuries as denominations multiplied and people needed words for shared faith.
Correligionist is a beautiful word that acknowledges we're part of communities defined by belief—it's the opposite of being alone in faith, showing how religion has always been about finding your people.
Complete word intelligence in one call. Free tier — 50 lookups/day.