Lean Sigma, or Lean Six Sigma is the term used to describe a combination of 'Lean' or Toyota Production Systems approaches with 'Six Sigma' the improvement approach developed by Motorola and later adopted by GE and other companies.

The advantage of combining the two approaches is that where Lean focuses on the removal of waste and reducing lead times, Six Sigma focuses on developing capable processes through the Define, Measure, Analyse, Improve, Control (DMAIC) cycle.  

In order to develop lean flow, processes must be standardised and capable, and Six Sigma re-emphasises the discipline of process capability studies and statistical process control.

Six Sigma is also very project focused, and provides useful project management discipline in implementing lean manufacturing improvements. Lean Sigma is therefore a project based approach to Lean, emphasising process capability and standardisation.

The term 'Lean Sigma' has been trademarked in the UK by Smallpiece Enterprises Ltd.