It depends on the type of plan and whether you are still employed by the plan sponsor. For a qualified workplace plan, you are exempt from the penalty if you terminated service with the employer when you were age 55 or older. If you are still employed with the plan sponsor, then the age for a withdrawal without the penalty is 59 1/2.
https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-tax-on-early-distri...
