Monkeypox is re-emerging and spreading over the world, posing a serious threat to human life, especially in non-endemic countries, including Saudi Arabia. Due to the paucity of research on knowledge about monkeypox in Saudi Arabia, this study aimed to evaluate the general population’s knowledge of monkeypox in a sample of the country. A web-based cross-sectional survey was conducted from 25 May 2022 to 15 July 2022. Participants’ knowledge about monkeypox on a 23-item scale and socio-demographic characteristics were gathered in the survey. Pearson’s Chi-square test was used to compare knowledge level (categorized into high and low) and explanatory variables. Out of 480, only 48% of the respondents had high knowledge (mean score > 14). Participants’ age, marital status, residential region, living in the urban area, education level, employment status, being a healthcare worker, income, and smoking status were significantly associated with the level of knowledge about monkeypox (p < 0.01). Overall, social media (75.0%) was the most frequently reported source from where participants obtained monkeypox-related information followed by TV and radio (45.6%), family or friend (15.6%), and healthcare provider (13.8%). We found that overall knowledge of monkeypox infection was slightly poor among the Saudi population. These findings highlight the urgent need for public education on monkeypox to promote awareness and engage the public ahead of the outbreak.