The 3rd IEEE International Workshop on Reliability and Security Data Analysis (RSDA 2016) is co-located with the 46th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN 2016) being held in June 28 - July 1, 2016, Toulouse, FRANCE. Computer systems are the basis for daily human activities and, more importantly, they play a key role in a variety of critical domains. Assessing dependability properties of computer systems is today an important concern for engineers and practitioners. The analysis of textual/numeric data and log files produced under real workload conditions by applications, systems, and networks, intrusion detection systems, monitors and issue-trackers plays a key role for dependability assessment. Data analysis is crucial in a variety of engineering tasks, such as measuring availability and reliability of a system, characterizing failures, gaining insights into the progression of security attacks, designing mitigation means and countermeasures. Academia and industry widely recognize the inherent potential of reliability and security data analysis for assessing dependability of computer systems and operational networks, and improving the engineering process. Data analysis in these specific areas poses many challenging research questions due to the heterogeneity, volume and velocity of the collected data, the lack of systematic end-to-end analysis procedures, the increasing diversity of analysis objectives and emerging application domains in critical areas.