The 6th Int'l Conference on Quantum Algorithms and Complexity Theory (QACT 2026) will be held in Xiamen, China, during May 29-31, 2026. The aim of QACT is to provide a stage for researchers, engineers, academicians as well as industrial professionals from all over the world to present their research results and development activities in Quantum Supremacy and Advantage, Quantum Machine Learning, Quantum Complexity Classes, Topological Quantum Computing, Distributed Quantum Computing, etc. QACT 2026 will be a valuable and important platform for inspiring international and interdisciplinary exchange at the forefront of Quantum Algorithms and Complexity Theory. Xiamen is an island city with a rich and dramatic history, replete with pirates, rebel leaders, and European merchants. Now linked to mainland Fujian by a causeway, Xiamen retains a strong international flavor. Known in the West as Amoy, Xiamen has a long history as a port city, and later became a center of British trade in the 19th century. Their foreign settlements, later taken over by Japanese invaders at the start of World War II, were established on the nearby small Gulangyu Island. Many of the old treaty-port and colonial buildings in Western styles survive. Xiamen was declared one of China’s first Special Economic Zones in the early 1980’s, taking advantage of the city’s heritage as a trading center and the proximity to Taiwan. Today Xiamen is one of China’s most attractive and best-maintained resort cities. On behalf of the Organizing Committee, we cordially invite you to participate in QACT 2026. We look forward to seeing you in Xiamen!