RotCurveTool simulates and fits Galactic Rotation Curves (GRCs) using a modular framework of physically motivated mass models. The code directly analyzes raw observational data from tabulated sources or raw FITS velocity maps by modeling contributions from the bulge, disk, and dark matter halo using Hernquist, de Vaucouleurs, exponential disk, Navarro-Frenk-White (NFW), and Burkert profiles. The tool supports three fitting techniques: non-linear least squares, bootstrap resampling, and Markov Chain Monte Carlo (MCMC) with full uncertainty propagation. RotCurveTool outputs best-fit parameters, confidence intervals, and a suite of diagnostic plots including rotation curve fits, residuals, and posterior distributions. It addresses long-standing challenges in GRC analysis, including rigid model architectures, poor error handling, and lack of component-wise transparency, and is suitable for both pedagogical and research applications in galactic dynamics and dark matter studies.