"Rob has been an outstanding editor of the MEN and the skill and sensitivity with which he steered the coverage of last year’s Arena atrocity, championing the incredible spirit of Manchester, was testament to that," said Trinity Mirror Regionals editorial director Alan Edmunds.
"He leaves with our huge thanks and very best wishes."
The MEN website is now the largest regional news site in the UK in terms of daily and monthly audiences, says Trinity Mirror.
Rob said: "It has been a privilege to be editor of the Manchester Evening News and to have led such a talented team of journalists.
"We have tackled the ever-changing landscape of multi-media journalism to build a local, national and global audience. What matters to our readers matters to us.
"We offered a place for the people of Greater Manchester to come together when our city suffered a murderous act of terror which claimed 22 innocent lives in May last year. We raised millions of pounds for the bereaved and those most affected, and through our We Stand Together campaign we are helping to heal our city's wounds.
"Now it's time for me to hand over the reins."
Darren Thwaites, currently editor-in-chief of Trinity Mirror North East, will move across to take over from Rob as editor-in-chief of MEN/Huddersfield at the end of March.
At the same time Neil Hodgkinson, editor-in-chief of Humber and Lincolnshire, will widen his brief to include the North East.
Helen Dalby and Sarah Lester, heads of digital in the North East and Manchester respectively, will also step up to become the senior editor in their centres.
"Darren is one of our leading editors-in-chief and will be terrific in his new role", said Edmunds.
"He knows the region very well, having started his career on the Huddersfield Examiner, and is relishing such a fantastic opportunity. Darren pioneered our hyperlocal strategy when editor in Teesside and led the implementation of our digital-first newsroom model in Newcastle ahead of it being rolled out across our regional centres.
"Neil's vast experience and skill also equip him brilliantly to make the most of the new opportunities created by leading a wider region.
"I'm also delighted for Helen and Sarah. They have both been key to much of our digital success and will do a superb job of helping to lead us through more change.”