Dokar farko ta Newton, wacce aka fi sani da Law of Inertia, wata ka'ida ce ta asali ta ilimin kimiyyar lissafi da ke cewa abin da ke hutawa zai kasance yana hutawa, kuma abin da ke motsi zai ci gaba da tafiya tare da saurin gudu, sai dai idan an yi aiki da shi. ta wani karfi na waje. Wannan doka ɗaya ce daga cikin dokoki guda uku da Sir Isaac Newton ya gabatar a cikin littafinsa "Mathematical Principles of Natural Philosophy," wanda ya zama tushen tushen makanikai na gargajiya. Ainihin, doka ta farko ta bayyana cewa abubuwa sun saba yin tsayayya da canje-canje a yanayin motsinsu, ko na hutawa ne ko a motsi.