Yes, Lemonade is a legitimate renters insurance company. They're a relatively new insurer, and their business model has some interesting differences from most other renters insurance providers — for example, they handle most renters insurance claims through their mobile app, and they donate a portion of their profits to charities chosen by their customers.
However, in most respects, renters insurance from Lemonade functions the same as renters insurance from any other major insurance company. If they operate in your area and you need to buy renters insurance, you can get a quote from their website and see how their price measures up against their competitors, or read our review of Lemonade's renters insurance for more info.