Sola Fide, meaning 'faith alone,' is a theological doctrine established by Martin Luther that asserts that faith in Jesus Christ is the only means by which an individual can attain salvation. This principle challenged the Catholic Church's teachings on salvation, which included the necessity of good works and the sacraments as essential components. Sola Fide became a foundational belief for Protestantism and significantly influenced the Protestant Reformation, emphasizing personal faith over institutional mediation.