A Gram-stain-negative, microaerophilic strain, 80(YS1)T, with a spiral-shaped morphology and 1-2 sheathed flagella at each end of the cells was isolated from the gastric mucosa of Marmota himalayana, the animal reservoir of Yersinia pestis in China, on the Qinghai-Tibet Plateau. The strain grew at 30, 35 and 42 °C, but not at 25 °C. Growth was in the form of a thinly spreading film on brain heart infusion agar containing 8 % sheep blood under microaerobic conditions. The strain did not hydrolyse urea or hippurate, and did not grow on media containing 1 % glycine. It reduced nitrate to nitrite, and was catalase- and alkaline-phosphatase-positive, susceptible to nalidixic acid and resistant to cefalotin. It was positive for genus-specific PCR for the genus Helicobacter, but could not be classified to any recognized species according biochemical tests results. Therefore, a phylogenetic study based on 16S rRNA, 23S rRNA, 60 kDa heat-shock protein (hsp60) and gyrase subunit B (gyrB) genes was conducted. The 16S rRNA gene sequence (1468 bp) analysis showed that strain 80(YS1)T was most closely related to Helicobacter marmotae (96.7 % similarity). The 23S rRNA gene sequence (2879 bp) analysis showed that the strain was most closely related to Helicobacter canis (96 % similarity). The complete gyrB gene sequence (2325 bp) analysis showed that it was related phylogenetically to Helicobacter cinaedi (79.4 % similarity) and H. marmotae (79.1 % similarity). Analysis of the partial sequence of the hsp60 gene of strain 80(YS1)T showed closest similarity to the sequences of Helicobacter equorum (82 %) and H. cinaedi (81 %), respectively. However, there was no hsp60 sequence of H. marmotae available for analysis. The data of morphological, biochemical and phylogenetic characteristics all supported that this strain represents a novel species. The name Helicobacter himalayensis sp. nov. is proposed for this novel species with the type strain 80(YS1)T ( = CGMCC 1.12864T = DSM 28742T).