The open access book set LNCS 16556 + 16557 constitutes the refereed proceedings of the 27th International Symposium on Formal Methods, FM 2026, held in Tokyo, Japan, during May 18â€"22, 2026. The proceedings also include 4 invited talks, 8 tutorial papers, and 9 papers from the industry day track. and Main Track (1)Part II: Main Track (2);