Ennis, the former editor of Reveal's stablemate Best, replaces Michael Butcher, who resigned in August because of a family illness.
She will take up the position from 26 October and work alongside Butcher for a week before his departure on 30 October.
Ennis has edited Best magazine since April this year.
She was previously the editor of Now magazine from 1996 to 2007, and, following that, she worked as a magazine and newspaper consultant, and worked on the relaunch of the Daily Mail Weekend magazine, First magazine and Hair magazine.
NatMag is currently searching for Ennis’ replacement at Best.
NatMag’s managing director, Jessica Burley, said: "The role of editor on Reveal has attracted huge interest from a number of talented candidates but Jane's experience in this sector is second to none.
"Jane's contact book, skill and experience will ensure that Reveal continues to grow rapidly and deliver the scale that advertisers expect and the entertainment consumers demand."