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The Galactic blue supergiant SBW1 with its circumstellar ring nebularepresents the best known analog of the progenitor of SN 1987A. High-resolutionimaging has shown H-alpha and IR structures arising in an ionized flow thatpartly fills the ring's interior. To constrain the influence of the stellarwind on this structure, we obtained an ultraviolet (UV) spectrum of the centralstar of SBW1 with the HST Cosmic Origins Spectrograph (COS). The UV spectrumshows none of the typical wind signatures, indicating a very low mass-lossrate. Radiative transfer models suggest an extremely low rate below 10$^{-10}$Msun/yr, although we find that cooling timescales probably become comparable toor longer than the flow time below 10$^{-8}$ Msun/yr. We therefore adopt thislatter value as a conservative upper limit. For the central star, the modelyields $T_{\rm eff}$=21,000$\pm$1000 K, $L\simeq$5$\times$10$^4$ $L_{\odot}$,and roughly Solar composition except for enhanced N abundance. SBW1's very lowmass-loss rate may hinder the wind's ability to shape the surrounding nebula.The very low mass-loss rate also impairs the wind's ability to shed angularmomentum; the spin-down timescale for magnetic breaking is more than 500 timeslonger than the age of the ring. This, combined with the star's slow rotationrate, constrain merger scenarios to form ring nebulae. The mass-loss rate is atleast 10 times lower than expected from mass-loss recipes, without any accountof clumping. The physical explanation for why SBW1's wind is so weak presentsan interesting mystery.

UV spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analog