The primary function of a load balancer in cloud computing is to distribute network traffic across multiple servers. This ensures that no single server becomes overwhelmed, enhancing performance and reliability. By managing the workload, a load balancer helps maintain optimal resource utilization, improve responsiveness, and prevent downtime. It can also provide features like health monitoring, redirecting traffic away from non-responsive servers. Overall, load balancers play a crucial role in maintaining the availability and scalability of applications hosted in cloud environments.