Abstract Background The triglyceride–glucose index (TyG index), an alternative indicator of peripheral insulin resistance (IR), is associated with cardiovascular disease (CVD) in the general population. The aim of this research was to determine the correlation between early-onset stroke and the TyG index among young Chinese adults. Methods Participants (age ≤ 40 years) who attended their first physical examination in Kailuan General Hospital or its 11 subsidiary hospitals between 2006 and 2012 were enrolled. The subjects were divided into four equal points according to the quartile of the TyG index, with the lowest quartile (Q1) as the reference group. A Cox proportional hazard model was employed to assess the correlation between early-onset stroke incidence and the TyG index. Restricted cubic spline analysis was further conducted to examine nonlinear associations. The TyG index was calculated as Ln [Triglyceride (TG, mg/dL) × Fasting Blood Glucose (FBG, mg/dL)/2]. Results Overall, 35,999 subjects met the inclusion criteria. Their mean age was 30.8 ± 5.7 years, and 77.1% of subjects were males. During a median observation period of 11 years, 281 stroke events occurred (62 hemorrhagic strokes and 219 ischemic strokes). Compared to the Q1 group (as the lowest group), subjects in groups Q2-Q4 had significantly higher risks of early-onset stroke (P