The 6th workshop on Many-Task Computing on Clouds, Grids, and Supercomputers (MTAGS) will provide the scientific community a dedicated forum for presenting new research, development, and deployment efforts of large-scale many-task computing (MTC) applications on large scale clusters, Grids, Supercomputers, and Cloud Computing infrastructure. MTC, the theme of the workshop encompasses loosely coupled applications, which are generally composed of many tasks (both independent and dependent tasks) to achieve some larger application goal. This workshop will cover challenges that can hamper efficiency and utilization in running applications on large-scale systems, such as local resource manager scalability and granularity, efficient utilization of raw hardware, parallel file system contention and scalability, data management, I/O management, reliability at scale, and application scalability. We welcome paper submissions on all theoretical, simulations, and systems topics related to MTC, but we give special consideration to papers addressing petascale to exascale challenges. Papers will be peer-reviewed, and accepted papers will be published in the workshop proceedings as part of the ACM digital library (pending approval). The workshop will be co-located with the IEEE/ACM Supercomputing 2013 Conference in Denver Colorado on November 17th, 2013.