We report a continuous-wave (cw), intracavity, singly resonant optical parametric oscillator (ICSRO) based on an Yb:KYW laser pumped by a single-mode laser diode (LD). Pumping the ICSRO by a low-noise single-mode LD, combined with the reduced heat generation due to the lower quantum defect of the Yb:KYW laser system, effectively eliminated the onset of relaxation oscillations, which have been a long-standing problem in previous multimode-LD-pumped ICSROs, and resulted in a cw ICSRO being operated free of relaxation oscillations. At an LD power of 515 mW, the generated idler power was 21 mW at ∼3500 nm. To the best of our knowledge, this is the first demonstration of a single-mode-LD-pumped ICSRO.