You can generally access your 401(k) funds without penalty starting at age 59½. If you withdraw money before then, you usually face a 10% early withdrawal penalty plus taxes, unless you qualify for specific exceptions. One key exception is the IRS "rule of 55," which allows you to take penalty-free withdrawals from your 401(k) if you leave your job during or after the calendar year you turn 55 (50 for certain public safety employees). However, you must withdraw only from the 401(k) plan of your most recent employer, and the money must remain in that plan for the penalty exemption to apply. Other exceptions where you can withdraw from your 401(k) without penalty before age 59½ include:

• Hardship withdrawals for immediate and heavy financial needs (though taxes still apply)
• Disability or death
• Unreimbursed medical expenses above a threshold
• A series of substantially equal payments
• Certain military service, IRS levy, qualified domestic relations orders, etc.

After age 59½, you can withdraw without the 10% penalty but will owe ordinary income taxes on traditional 401(k) withdrawals. Required minimum distributions (RMDs) start later, typically at age 73 or 75 depending on birth year (though Roth 401(k)s do not have RMDs). In summary, typical access age is 59½, with some exceptions like the rule of 55 allowing earlier access without penalty if you leave your job after age 55.