Oryza longistaminata with strong resistance to biotic and abiotic stress was regarded as an excellent gene pool for Asian cultivated rice improvement. Thus, mining and utilization of favorable genes/alleles from O. longistaminata would be important in breeding for Oryza sativa by broadening its genetic basis. To explore blast resistance genes from O. longistaminata , RD23, an indica cultivar from Thailand, was crossed with an accession of O. longistaminata and a set of BC 3 F 7 introgression lines (ILs) was raised. The ILs were screened for blast resistance in natural blast nursery, and three ILs exhibiting high level of resistance to blast disease were obtained. Using a BC 4 F 2 population of IL-E1454/RD23, a novel dominant blast resistant gene, designated as Pi57 (t), was mapped on rice chromosome 12 flanked by SSR markers RM27892 and RM28093 within 1.0 cM. Pi57 (t) conferred a broad-spectrum resistance to Magnaporthe oryzae isolates collected from Yunnan, P. R. China, and the resistant spectrum was distinguished from five known blast R genes located on chromosome 12. Our results suggest that Pi57 (t) would be a promising gene for rice improvement in Yunnan, P. R. China.