Neytron (anglisi neutron, az lotini neuter — na inu na on, ishoratash p), zarrai elementarii khunso (bezaryad)-i massai sukunatash tp = = (1,674920±0,000011) • 10 kg, spinash 1/2/ (bo vohidhoi h =h/2P ), in jo h— sobitai Plank va momenti magnitiash Rt — — (1,91315±; 0,00007). Mya (Mya—magnetoni yadro). Neytronro olimi anglis Jeyms Chedvik kashf kardaast (1932). Yadroi hamai atomho az Neytronho va protonho tarkib yoftaast. Khosiyathoi Neytron va proton ba hamdigar monandand, ki dar barobarii spinhoshon, nazdik budani massai sukunatashon, qobiliyati ba hamdigar mubaddalshaviashon (masalan, hangomi beta-kohish), hamchunin ba zaryad novobasta budani quvvahoi yadroi zohir megardand.
In khosiyatho imkon medihand, ki Neytron va protonro chun du holati (elektri zaryadnok va bezaryad) yak zarra — nuklon muoina kunem. Neytron dar holati ozod noustuvor ast: on bo davri nimkohishi T1/2=(1,01±0,03).10e soniya ba proton, elektron na antineytrino judo meshavad. Neytronho ba cap zadani reaksiyahou yadroy, az on jumla, reaksiyai zanjirii taqsimshavii yadrohoi vaznin (toriy, uran, plutoniy), ki dar reaktorkhoi yadroi ba a mal meoyand, bois msgardad. Neytronhoro baroi hosil kardani izotophoi radioaktivi suni va dar neytronografiya istifoda mebarand. Antizarrai Neytron antineytron ast, ki az Neytron bo alomati momenti magnitiash farq mekunad.