In the historic heart of Sag Harbor - a village shaped by its storied whaling past and now celebrated for its cultural sophistication - Residence A stands as a singular architectural statement along one of the most coveted stretches of waterfront. Commanding approximately 250 feet of prime frontage on the harbor, this exceptional estate is far more than a home; it is a four-level masterwork of glass, stone, and light, created for a global buyer seeking complete privacy, effortless luxury, and direct nautical access. This extraordinary property is the result of a visionary collaboration between J. Bialsky of Bialsky Premiere Design & Development and the internationally acclaimed Hollander Design Landscape Architects. Together, they have crafted a residence that exists in perfect harmony with the Peconic Bay - a seamless dialogue between architecture, landscape, and water. Every line is intentional, every perspective framed, and every material selected to endure the coastal environment while maintaining an elevated, timeless aesthetic. Spanning an impressive 16,974 square feet across four levels, the estate is conceived as a vertical sanctuary where grand-scale entertaining and intimate retreat coexist effortlessly. Interiors encompass approximately 12,551 square feet of meticulously designed living space, defined by a palette of organic textures, refined finishes, and state-of-the-art systems. The residence offers eight expansive bedroom suites and ten beautifully appointed baths, thoughtfully arranged to accommodate guests, and live-in staff with complete comfort and privacy. Outdoor living unfolds across multiple levels of tiered terraces and lounge decks, creating a dynamic al fresco experience that keeps the water constantly within view. At the pinnacle, a private rooftop sanctuary serves as a crowning architectural achievement - featuring a pool and spa seemingly suspended above the harbor, offering uninterrupted 360-degree vistas and breathtaking sunset views across Sag Harbor's golden coastline. For the yachting enthusiast, the property delivers a level of functionality rarely found in village waterfront estates. A private, deep-water marina includes two 60-foot boat slips, placing you at the center of the Hamptons' maritime lifestyle with immediate access to the open Atlantic and the protected waters of Shelter Island Sound. Beyond its beauty, the residence operates with the precision of a modern high-security retreat. A rare private garage provides secure parking in the heart of the village, while fully integrated smart-home technology manages climate, lighting, and security seamlessly from anywhere in the world. Turn-key in every sense, Residence A represents a rare convergence of location, design pedigree, and waterfront capability - an exceptional offering for the most discerning buyer seeking a legacy property in one of the Hamptons' most iconic destinations.