Superconducting detectors have become essential devices for high-performance single-photon counting over a wide wavelength range with excellent time resolution. Detector fabrication typically relies on resist-based lithography processes, which can limit possibilities for device integration, e.g., on unconventional substrates. Here, we demonstrate a resist-free fabrication route for realizing superconducting nanowire single-photon detectors based on focused electron beam-induced deposition. Utilizing direct writing of a Pt–C mask, we achieved nanowire meanders with linewidths below 100 nm, operated them as superconducting devices for the detection of visible and near-infrared photons, and showed detector integration on side-polished optical fibers. Being compatible with device fabrication on curved irregular surfaces, our approach could enable superconducting detector integration in complex configurations.