Understanding edge effects and quantifying their impact on the carrier properties of two-dimensional (2D) semiconductors is an essential step toward utilizing these materials for high performance electronic and optoelectronic devices.1-5 WS2 monolayers patterned into disks of varying diameters are used to experimentally determine the influence of edges on their optical properties. Carrier lifetime measurements show a decrease in the effective lifetime, τeffective, as a function of decreasing diameter, suggesting that the edges are active sites for carrier recombination. Accordingly, we introduce a metric called edge recombination velocity (ERV) to characterize the impact of 2D material edges on non-radiative recombination. The unpassivated WS2 monolayer disks yield an ERV ∼ 4 × 104 cm/s. This work quantifies the non-radiative recombination edge effects in monolayer semiconductors, while simultaneously establishing a practical characterization technique towards experimental explorations of edge passivation methods for 2D materials.