Two Gram-negative, non-spore-forming, oval to pear shaped motile strains, designated 25B14_1(T) and BH-BN04-4(T), isolated from surface seawater from the Bering Sea and Chukchi Sea, respectively, were subjected to polyphasic taxonomic study. Phylogenetic analysis based on 16S rRNA gene sequences demonstrated that strains 25B14_1(T) and BH-BN04-4(T) clustered together with Hyphomonas atlanticus 22II1-22F38(T) and Hyphomonas oceanitis DSM 5155(T), respectively, within genus Hyphomonas. Based on whole genome sequence analysis, the calculated DDH and ANIm values between strain 25B14_1(T) and BH-BN04-4(T) are 18.8 and 83.19% respectively. The calculated DDH values of strain 25B14_1(T) and BH-BN04-4(T) with seven type strains ranged from 18.2 to 19.9% and from 18.4 to 40.4%, respectively. The ANIm values of strain 25B14_1(T) and BH-BN04-4(T) with seven type strains ranged from 83.00 to 84.67% and from 83.14 to 90.58%, respectively. Both isolates were found to contain Q-11 as the predominant respiratory quinone. The major fatty acids of strain 25B14_1(T) were identified as C(16:0), C(17:0), C(18:1)ω7c-methyl and Summed Feature 8 (C(18:1)ω6c/ω7c as defined by MIDI), while in the case of strain BH-BN04-4(T) they were identified as C(16:0), C(18:1)ω7c-methyl and Summed Feature 8 (C(18:1)ω6c/ω7c). The G+C contents of 25B14_1(T) and BH-BN04-4(T) were determined to be 58.4 and 61.0 mol%, respectively. The combined phenotypic and genotypic data show that the two isolates each represent novel species of the genus Hyphomonas, for which the names Hyphomonas beringensis sp. nov. and Hyphomonas chukchiensis sp. nov. are proposed, with the type strain 25B14_1(T) (=MCCC 1A07321(T) = LMG 27914(T)) and BH-BN04-4(T) (=MCCC 1A07481(T) = LMG 27915(T)), respectively.