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Abstract Among Neptunian mass exoplanets (20−50M_⊕), puffy hot Neptunes are extremely rare, and their unique combination of low mass and extended radii implies very low density (ρ< 0.3 g cm⁻³). Over the last decade, only a few puffy planets have been detected and precisely characterized with both transit and radial velocity observations, most notably including WASP-107b, TOI-1420b, and WASP-193b. In this paper, we report the discovery of TOI-1173 Ab, a low-density ( $\rho ={0.195}_{-0.017}^{+0.018}$g cm⁻³) super-Neptune withP= 7.06 days in a nearly circular orbit around the primary G-dwarf star in the wide binary system TOI-1173 A/B. Using radial velocity observations with the MAROON-X and HIRES spectrographs and transit photometry from TESS, we determine a planet mass ofM_p= 27.4 ± 1.7M_⊕and radius ofR_p= 9.19 ± 0.18R_⊕. TOI-1173 Abis the first puffy super-Neptune planet detected in a wide binary system (projected separation ∼11,400 au). We explore several mechanisms to understand the puffy nature of TOI-1173 Aband show that tidal heating is the most promising explanation. Furthermore, we demonstrate that TOI-1173 Ablikely has maintained its orbital stability over time and may have undergone von-Zeipel–Lidov–Kozai migration followed by tidal circularization, given its present-day architecture, with important implications for planet migration theory and induced engulfment into the host star. Further investigation of the atmosphere of TOI-1173 Abwill shed light on the origin of close-in low-density Neptunian planets in field and binary systems, while spin–orbit analyses may elucidate the dynamical evolution of the system.