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There is an increasing need to simplify optical coupling techniques for low-temperature integrated photonics experiments. Various promising and scalable photonic packaging techniques have been under development, but few methods compatible with low-temperature operation have been reported. Here, we demonstrate 25% coupling efficiency from an optical fiber to a silicon optomechanical crystal at 7 mK in a dilution refrigerator without in-situ optical alignment at cryogenic temperatures. Our coupling scheme uses angle-polished fibers glued to the surface of the chip. The technique paves the way for scalable integration of optical technologies at low temperatures, circumventing the need for optical alignment in a highly constrained cryogenic environment. The technique is broadly applicable to studies of low-temperature optical physics and to emerging quantum photonic technologies.