Na may refer to:

• Na (kana), a Japanese kana
• Na (tree) or Mesua ferrea, a species of tree native to Sri Lanka
• .na, the top-level domain for Namibia
• Na people, a small tribal group in India
• Mosuo or Na, a small ethnic group in China near Tibet
• Nauruan language, ISO code
• Sodium's chemical symbol
• Avogadro constant, N_A

.na is the Internet country code top-level domain (ccTLD) for Namibia. Registry/Registrar Separation has been implemented, with Namibian and Foreign Registrars being accredited. The Registry supports a Web/GUI interface and EPP.

Potassium-dependent sodium-calcium exchanger also known as solute carrier family 24 (SLC24) is a type of sodium-calcium exchanger that requires potassium to function.

Sodium ( ) is a chemical element with the symbol Na (from ) and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is ²³Na. The free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as feldspars, sodalite and rock salt. Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that chloride and sodium are the most common dissolved elements by weight in the Earth's bodies of oceanic water.