13C hyperpolarization has opened the door for real-time MR metabolic imaging but remains limited by T1's of approximately one minute or less. 15N offers potentially much longer T1's, but suffers from poor intrinsic sensitivity and small chemical-shift separation. We have hyperpolarized L-[15N]carnitine-d9, a novel metabolic imaging probe, and found ultra-long T1's of 210s (in H2O) / 160s (in vivo). We also demonstrate successful 15N->1H hyperpolarization transfer for enhanced sensitivity of detection as well as larger chemical-shift separation among metabolites. The long signal lifetime and excellent safety profile of [15N]carnitine suggest great potential for metabolic imaging investigations and future clinical translation.