Last season's treble winners emphatically rounded off their campaign with four scores before the break.
James Segeyaro and Brett Ferres both scored tries, and Jimmy Keinhorst went over twice within four minutes.
Three more followed in the second half while Leigh secured consolations through Sam Hopkins and Matty Dawson.
Both sides knew their 2017 Super League status was secure before kick-off, with top spot in the Qualifiers up for grabs.
But Championship winners Leigh, who will return to the top tier for the first time since 2005, were also aiming to complete a 20-match winning run.
Leeds ended any hopes of that as they raced into an 18-0 lead before Hopkins got Leigh on the board.
The Rhinos' stranglehold continued in the second half and stand-off Joel Moon finished off another fine counter-attacking try, engineered by breaks from Ashton Golding and Segeyaro.
Leeds Rhinos coach Brian McDermott: "It's been my toughest year in rugby league, for sure.
"When I coached down at London it was hard yards but there was always a pot of gold at the end of the rainbow that I was always chasing.
"There didn't seem to be an answer this year.
"I stayed on the rock face. I wasn't sure if I could climb up and I knew climbing down wasn't an option, but dropping off is absolutely not an option."
Leigh Centurions coach Neil Jukes: "We're naturally disappointed.
"But, when we sit back next week in Portugal watching the Million Pound Game with free beer off our owner, as a squad and staff, we'll celebrate this season."
Leeds Rhinos: Golding, T. Briscoe, Watkins, Keinhorst, Hall, Sutcliffe, Moon, Singleton, Segeyaro, Jones-Buchanan, Ferres, Ward, Cuthbertson.
Replacements: Handley, Hallas, Smith, Jordan-Roberts.
Leigh Centurions: Smith, Brown, Worthington, Tonga, Dawson, Ridyard, Drinkwater, Moimoi, Higham, Weston, Dixon, Maitua, Hock.
Replacements: Hansen, Hopkins, Burns, Tickle.
Referee: Gareth Hewer (RFL)
Attendance: 14,747
Leeds Rhinos ran in seven tries to top the Qualifiers and deny Leigh Centurions a perfect record in the Super League promotion competition.