Region One may refer to:

• The Barima-Waini region of Guyana
• Region One School District in Connecticut, USA
• Region 1 DVD

• Plasmodium jiangi
• Plasmodium josephinae
• Plasmodium joyeuxi
• Plasmodium kentropyxi
• Plasmodium knowlesi transmission
• Plasmodium lacertiliae
• Plasmodium lainsoni
• Plasmodium lemuris
• Plasmodium lepidoptiformis
• Plasmodium lionatum
• Plasmodium lutzi
• Plasmodium lygosomae
• Plasmodium mackerrasae
• Plasmodium maculilabre
• Plasmodium marginatum
• Plasmodium melanipherum
• Plasmodium mexicanum
• Plasmodium michikoa
• Plasmodium minasense
• Plasmodium octamerium
• Plasmodium osmaniae
• Plasmodium papernai
• Plasmodium paranucleophilum
• Plasmodium pelaezi
• Plasmodium percygarnhami