Troubleshooting Mule refers to the process of identifying, diagnosing, and resolving issues or errors in MuleSoft integration applications developed using Mule runtime engines. Troubleshooting involves analyzing log files, monitoring message flows, and debugging integration components, connectors, and transformers to identify root causes of integration failures or unexpected behaviors. Troubleshooting techniques help developers resolve issues and ensure the reliability and performance of MuleSoft integrations.