An aerobic methanotroph, strain Kb3^T, was isolated from a rhizospheric soil sample collected from a tropical Indian rice field. The cells were motile, Gram-negative bacilli, formed pink colonies and pink turbid/pellicles in the liquid medium. Biochemical characteristics showed that strain Kb3^T utilised only methane and methanol as its sole carbon and energy sources. The isolate's 16S rRNA gene sequence expressed 99.52% similarity to the recently described valid species Methylomonas fluvii EbB (Mmf), with 92% query cover. But examining the genome similarity between Kb3 and EbB, a DDH value of 44.20% [41.6 - 46.7%] and an Ortho-ANI value of 91.48 was observed that were below the current cut-off values for species differentiation. Also, the 16S rRNA gene phylogeny and the phylogenomic analysis branched the two species separately. The major fatty acid in Methylomonas sp. Kb3 was C_14:0, followed by C_16:1 ω5c. The genome sequence revealed the size of strain Kb3 is 5.1 Mb, with the G + C content of 51.8%. Strain Kb3^T shared the closest relatedness with Methylomonas sp. LW13 reveals a 99.66% 16S rRNA gene similarity, an Ortho-ANI value of 97.9%, a DDH value of 87.3%, and a close branching in the phylogenomic tree Kb3 and LW13 together form a new species. The genomic and phylogenetic distinction between species Mmf and strain Kb3 supports Kb3^T to be described as a novel species within the genus Methylomonas, with the proposed name, Methylomonas aquatica sp. nov. (Mma) and the type strain being Kb3^T (=MCC 4012, =JCM 33634, =KCTC 72521).