Class I
# Class I

Class I may refer to:

* Class I antiarrhythmic
* Class I electrical appliance, a device constructed according to electrical grounding specifications in the IEC 60536-2 standard
* Class I bacteriocin, a type of toxin produced by some bacteria
* Class I biosafety cabinet
* Class I laser, a type of eye-safe laser defined in the ANSI Z136 standard
* Class I rail carrier, a type of major freight railroad company in Canada
* Class I railroad, a type of major freight railroad company in the United States
