The newton second (symbol N s or N·s) is the derived SI unit of impulse and momentum. It can also be expressed as the kilogram metre per second (kg·m/s). One newton second corresponds to a one newton force applied for one second. The newton second is occasionally, colloquially, referred to as a "sNewton."

It can be used to identify the resultant velocity of a mass if a force accelerates the mass for a specific time interval.