Abstract: The turbot (Scophthalmus maximus) is a marine fish of high commercial value and wildly cultured in Europe and China. Gonadotropin-releasing hormones (GnRHs), as a neuropeptide of sex hormone, stimulate synthesis and release of pituitary gonadotropins, inducing vertebrate gonads to provide sex steroids for the formation and maturation of gametes. Hence GnRH has been proven to be the key signal molecule in the hypothalamus-pituitary-gonadal axis. However, their dynamics expression and functional roles during the ovarian developmental in S. maximus remained not fully elucidated. The present study aimed to investigate the expression patterns and key subtype localization of GnRHs in the brain of turbot during ovarian developmental. Ovarian developmental stages and brain structures were identified using hematoxylin and eosin (H.E) staining. The mRNA levels of gnrhs in various brain regions during ovarian developmental were detected by quantitative real-time PCR (qRT-PCR). The structure of S. maximus brain exhibited a regular linear arrangement of the telencephalon, mesencephalon, cerebellum, hypothalamus, and medulla oblongata, with highly differentiated functions and the mesencephalon occupying the largest proportion. Ovarian development obtained the typical pre-vitellogenic, early-vitellogenic, late-vitellogenic, nuclear migration, and atresia stages. The mRNA levels of gnrh3 was peaked at the late-vitellogenic stage, while gnrh1 and gnrh2 were peaked at the nuclear migration stage. Meanwhlie, the mRNA levels of gnrh1 in all brain regions were significantly higher than those of other subtypes, the highest values were observed in the telencephalon at the nuclear migration stage. In situ hybridization further confirmed that gnrh1-positive signals were enriched in the ventral telencephalon and hypothalamus. Thus, the large relative area of the S. maximus mesencephalon confers enhanced visual information processing capacity, enabling adaptation to complex benthic environments. Moreover, the heightened expression of gnrh1 specifically in the telencephalon during the nuclear migration regulates the final maturation of oocytes, identifying it as the key subtype regulating ovarian development and maturation in S. maximus. This study systematically delineates the brain architecture of the S. maximus and uncovers the expression profiles of GnRH subtypes throughout ovarian development. These findings provide a crucial theoretical foundation for investigating neuroendocrine regulatory mechanisms and for the development of efficient reproductive management strategies in captivity.