No.  All of your personal contributions and all the earnings on your contributions are 100% nonforfeitable ("vested") and owned by you.  If your employment ends for any reason, the money is yours to take with you.

If your new employer sponsors a retirement plan, you may transfer the funds from your current employer directly to your new employer's plan.  If your new employer does not provide a retirement plan, you may transfer your funds directly to an Individual Retirement Account, in your name, thereby avoiding income tax on the distribution.

Please refer to QPA's Retirement Plan Rollover Chart for specific examples.