Nydahl is a surname.

• Ole Nydahl (b. 1941), a Danish teacher of Tibetan Buddhism
• Tomas Nydahl (b. 1968), a Swedish tennis player

• Cyanidin-3-rhamnosylglucoside 5-O-glucosyltransferase
• Cyanidioschyzon merolae strain 10D
• Cyanidioschyzon merolæ
• Cyanin (anthocyanin)
• Cyanines
• Cyanins
• Cyaniriodes libna
• Cyaniriodes siraspiorum
• Cyaniris acesina
• Cyaniris albocaeruleus
• Cyaniris beretava
• Cyaniris biagi
• Cyaniris camenae
• Cyaniris candaules
• Cyaniris cara
• Cyaniris cossaea
• Cyaniris dilectissima
• Cyaniris drucei
• Cyaniris kolari
• Cyaniris lugra
• Cyaniris lyseas
• Cyaniris parishii
• Cyaniris placidula
• Cyaniris plauta
• Cyaniris ripte