A systematic review of the incubation period of COVID-19 was compiled and analyzed from 21 quantitative studies. We investigated the incubation period of COVID-19 with regard to age, biological sex, location, and severity of the disease. Based on the data extracted, we report an overall mean and median incubation period for SARS-CoV-2 of 5.894 days and 5.598 days, respectively. The incubation period did not statistically vary for biological sex or age, but some studies suggest a longer incubation period in the young and elderly. Cases of COVID-19 in Wuhan and Hubei Province of China may have a shorter incubation period for COVID-19 but the shorter incubation period may be due to an increase in viral load. In studying coronavirus strains such as SARS and MERS, researchers have discovered an inverse relationship between incubation period length and virus severity. Taking into consideration that SARS-CoV-2 is part of the beta-coronavirus family, as well as the study mentioned above, we suggest that people who experience more severe disease due to SARS-CoV-2 may have a shorter incubation period.