A new and distinct cultivar of Chrysanthemum plant named `Tatyana`, characterized by its large decorative-type inflorescences with white-colored lanceolate-shaped ray florets; numerous ray florets and very few disc florets; disc florets typically inconspicuous; dark green-colored foliage; strong and upright flowering stems; low number of lateral branches which reduces the amount of disbudding required; short response time; and excellent postproduction longevity.