OpenTreeMap is a collaborative platform for crowdsourced tree inventory, ecosystem services calculations, urban forestry analysis, and community engagement. Funded in part by grants through the USDA Small Business Innovation Research program, OpenTreeMap encourages community groups, non-profit organizations, governments, and local citizens to work together to map and explore the urban forest. Members of the public can search existing tree data by species and other search filters, add new trees, edit tree data, upload images, or leave comments. OpenTreeMap uses the i-Tree software developed by the US Forest Service to calculate and display the ecosystem benefits generated by urban trees. OpenTreeMap is available as open source software or a subscription service, and there are over thirty-five OpenTreeMap sites available worldwide.