The Spiritual Eldering Institute (SEI) was a multi-faith, U.S.-based organization that focused on spiritual development, interpersonal relationships, communication, and service in later life. The Institute was dedicated to the spiritual dimensions of aging and conscious living as expressed in the work of Rabbi Zalman Schlachter-Shalomi. "Spiritual Eldering" was a phrase coined by Schachter-Shalomi after taking a 40-day retreat at Lama Foundation in New Mexico in preparation for his 60th birthday. Founded in Philadelphia with the writing (with Ronald Miller) of From Age-ing to Sage-ing, the SEI eventually moved to Boulder, Colorado. Due to financial difficulties, SEI was forced to shut-down in 2005, but the spiritual eldering movement persists and continues to work through The Sage-ing Guild. The terms Spiritual Eldering and Sage-ing are used synonymously and are trademarked by the Institute.

Gift of Rabbi Zalman M. Schachter-Shalomi in 2010 and Judith Helburn in 2013​.