It is 2 years for most injuries; please note the following:
If you are injured in California due to the negligence of another person, who is a private party, not a public entity, then you have up to two years from the date of accident to either settle your case or file a lawsuit to protect your legal rights to any potential monetary recovery against that person directly. If you do not, you will forever lose your legal rights to pursue an action in court.
Now, if you were injured by a government entity, like a city for example, then you have a six month statute of limitations to file your claim against the city. If your claim is then denied by the city, you generally have six more months from the date your claim was denied to file your lawsuit agains the city.
Finally, if you were injured on the job due to some person or some entity connected exclusively with your employer, then you have up to one year to file your injury claim to begin the process for your workers compensation benefits. If you were injured on the job by a third party not connected with your employer, you still have a one-year statute of limitations to file your workers compensation and then two years to file against a private third party, and six months to file against a government third party.
As you can see, different time frames apply depending on the type of your accident; you should consult an experienced California Personal Injury Attorney as soon as possible in order to protect your statute of limitations.