This paper investigates the impact of gig economy on labor unrest, by exploiting an exogenous shock from the staggered introduction of the leading online-to-offline (O2O) delivery platforms, Ele.me, into 245 major cities in China. Using a difference-in-difference approach, we find that the number of strikes and labor protest events is increased by around 31% in gig economy. The effect is more pronounced for firms in regions with weaker legal environment, with high gig economy search index, with higher entrepreneurship rates, and with better access to mobile internet. Our findings indicate that gig work opportunities serve as outside options for employees, which enhance their bargaining power over firms.