Introduction Noroviruses is a major cause of outbreaks and sporadic acute gastroenteritis (AGE) across all age groups. Although the GII.4 norovirus has been the primary cause of most AGE outbreaks, Non-GII.4 norovirus has been reported globally. AIM We aimed to report an increase in GII.17 norovirus outbreaks of acute gastroenteritis in multiple provinces of China during the second half of 2024. Methods Data and specimens from AGE outbreaks (January 2022–December 2024) were collected. Samples were tested via real-time RT-PCR; positive GII.17[P17] samples underwent sequencing and phylogenetic analysis. Results Among 1,579 NoV outbreaks, 1,225 were genotyped. The first half of 2022–2024 saw co-circulation of genotypes GII.3[P12], GII.4 Sydney, GII.17[P17], and GII.7[P7]. GII.4 Sydney dominated the second halves of 2022 (46.15%) and 2023 (51.63%). Strikingly, in the second half of 2024, GII.17[P17] became predominant, causing 75.28% of outbreaks. This shift was driven by a novel GII.17 variant (Romania-2021 like, subcluster C2), first detected in February 2024, which replaced the previous Kawasaki 308-like variant. The novel variant predominantly affected the 6–18 years age group (54.97%) and elementary schools (34.33%). It featured five amino acid mutations in epitopes and one in the histo-blood group antigen binding site, plus five deletions. Conclusions A novel GII.17 variant has overtaken GII.4 as the predominant norovirus strain in China since late 2024, underscoring the need for continued molecular surveillance.