Aims: Arterial stiffness is an important marker of cardiovascular risk, but repeated assessment of aortic pulse wave velocity (PWV) in daily life remains difficult using cuff-based devices alone. We investigated whether ring photoplethysmography (PPG) recorded overnight could serve as a practical vascular index by evaluating its session-wise association with cuff-based estimated aortic PWV. Methods: Continuous ring PPG signals were segmented into fixed 5-min windows immediately preceding each cuff-based measurement obtained using Mobil-O-Graph. For each session, beat-level PPG features were extracted and summarized into session-level descriptors reflecting pulse timing and waveform morphology. Candidate predictors included both raw session-level features and within-subject change features. Associations with estimated aortic PWV were examined using univariable analysis, followed by ridge regression with leave-one-subject-out (LOSO) validation. Results: A total of 209 sessions from 10 subjects were analyzed. Pulse-width-related features showed the strongest univariable associations with estimated aortic PWV. In LOSO evaluation, ridge regression improved subject-independent prediction performance and achieved a Pearson correlation coefficient (r) of 0.58, a mean absolute error (MAE) of 0.32, and a root mean square error (RMSE) of 0.41. Frequently selected predictors captured information on pulse width, amplitude, upstroke morphology, rise-decay balance, and within-subject heart rate change. These findings suggest that cuff-based estimated aortic PWV is associated not only with beat timing but also with pulse-width-related and upstroke-related waveform characteristics derived from ring PPG. Conclusions: Ring PPG showed a moderate and consistent session-level association with cuff-based estimated aortic PWV, supporting the feasibility of ring-only vascular surrogate monitoring during overnight recording.