Considerably roomier than the queen- or full-sized mattresses, the ever popular King mattress allows ample of room to really stretch out and relax. Although shorter than the California king, the standard king mattress is often wider, making it a great option for many people. Browse Costco’s expansive selection of king mattresses, which can be conveniently filtered by brand, firmness, and composition, Whether you’re looking for a luxuriously plush pillow top, body hugging ultra-firm support, or responsive multi-layer memory foam, you’ll find what you’re looking for at Costco. A great night’s sleep awaits!