Striking weight biases emerge early in development, yet cognitive-developmental research has largely ignored weight as a social characteristic of interest. How do children conceive of weight? In particular, do children hold essentialist views of weight (i.e. do they view weight as natural, stable, inductively meaningful, and reflective of people's insides) as they do of so many other social characteristics? We conducted an exploratory investigation of children's weight essentialism across two studies. In total, 356 participants (280 4- to 11-year-old children and 76 adults from the United States, mostly White and from middle- to high-income families) participated in three tasks, respectively assessing three dimensions of essentialism of social categories: Beliefs about weight stability, heritability, and inductive potential despite transformation. Results revealed that children viewed weight as stable (similarly so to race) and informative of someone's food choices, but they did not view it as biologically- or genetically-determined. Thus, children may not view weight as reflecting people's biological nature (biological essentialism), but they may view weight as reflecting people's stable personal character (moral essentialism) - a view which is also highly compatible with weight bias, unlike biological essentialism. Children also demonstrated stronger essentialist views of lightness than heaviness across tasks, though essentialism of heaviness increased over development. Findings are discussed as they relate to early conceptions of weight and weight bias. Implications for conceptualizations and measurement of essentialism are also discussed.