Yes, Coursera offers individual courses as well as Specializations spanning multiple courses that can prepare you for Six Sigma certification, as well as courses to provide you with additional tools to complement your Six Sigma (and and Lean Six Sigma) education.
Because these courses are offered by renowned institutions like the University of Georgia, the University of Amsterdam, and Rutgers the State University of New Jersey, you can learn online while maintaining a high level of quality control over your own education. Learning online also allows you to complete course materials on a flexible schedule, making them an ideal fit for working professionals that want to add new skills to their toolkit.