A large-scale reconfigurable reflect-array antenna (RRA) with 2-bit phase resolution is reported here at Ka -band. The unit cell is designed based on a segmented resonator with end folding, which facilitates cell miniaturization and offers a stable angular response. By incorporating only two PIN diodes into each RRA unit cell, 2-bit phase compensation can be obtained due to the electronical reconfigurability of the resonant current path length. In order to validate the properties of the proposed 2-bit cells, a free-space scattering measurement of a uniform array is conducted. Furthermore, in order to construct large-scale extensible RRAs to meet versatile application demands, modular reflect-subarrays, each containing 144 RRA cells and their control module, are utilized as constitutive building blocks. As a demonstrative example, a 1296-cell RRA prototype fed by a broadband planar array is synthesized, fabricated, and characterized, yielding a peak gain of 29.2 dBi and an aperture efficiency of about 27.1% at 26.1 GHz. It experimentally achieves a beam scanning coverage up to ±50° with a 3-dB scanning loss. The demonstrated RRA is a promising candidate for future millimeter-wave communication and radar systems.