ABSTRACT: Importance:Despite major differences in their health care systems, medical crowdfunding is increasingly used to finance personal health care costs in Canada, the UK, and the US. However, little is known about the campaigns designed to raise monetary donations for medical expenses, the individuals who turn to crowdfunding, and their fundraising intent. Objective:To examine the demographic characteristics of medical crowdfunding beneficiaries, campaign characteristics, and their association with funding success in Canada, the UK, and the US. Design, Setting, and Participants:This cross-sectional study extracted and manually reviewed data from GoFundMe campaigns discoverable between February 2018 and March 2019. All available campaigns on each country domain's GoFundMe medical discovery webpage that benefitted a unique patient(s) were included from Canada, the UK, and the US. Data analysis was performed from March to December 2019. Exposures:Campaign and beneficiary characteristics. Main Outcomes and Measures:Log-transformed amount raised in US dollars. Results:This study examined 3396 campaigns including 1091 in Canada, 1082 in the UK, and 1223 in the US. Campaigns in the US (median [IQR], $38?204 [$31?200 to $52?123]) raised more funds than campaigns in Canada ($12?662 [$9377 to $19?251]) and the UK ($6285 [$4028 to $12?348]). In the overall cohort per campaign, Black individuals raised 11.5% less (95% CI, -19.0% to -3.2%; P?=?.006) than non-Black individuals, and male individuals raised 5.9% more (95% CI, 2.2% to 9.7%; P?=?.002) than female individuals. Female (39.4% of campaigns vs 50.8% of US population; difference, 11.3%; 95% CI, 8.6% to 14.1%; P?