Young religions, also called New religious movements (NRMs) are religions created recently, examples like LaVeyan Satanism (1966), Thelema ( early 1900s), Latter Day Saints (LDS / Mormons, 1820s), Jehovah's Witnesses (JWs, late 1870s), Discordianism (1963)
Older religions include Judaism and Hinduism, etc
"Most recent" is difficult to answer, but the largest religion today is Christianity with over 2 billion followers, followed by Islam and then irreligion.