Guise, a member of the Sumner Running Club and the New Zealand ski mountaineering team, won the men's title in a time of 2hr 53min 20sec.
Wanaka's James Greenslade-Yeats (3hr 11min 10sec) was second and Queenstown real estate agent Baz Smith was third (3hr 13min 38sec).
Harper was the first woman home in 3hr 47min 3sec.
Second placegetter Kelly McFadzien was hot on Harper's heels, finishing in 3hr 49min 48sec, while third-placed Melanie Moran crossed the line at the Glenorchy end of the Routeburn Track in 3hr 51min 51sec.
There were 312 people entered in the Classic, a tough 32km run through Fiordland and Mt Aspiring national parks along the Routeburn Track.
Starting at 8am from the Divide on the Milford Rd, they faced a rainy day on the track.
Event director Evan McWhirter said the race, now in its seventh year, was a "textbook" Routeburn Classic.
"It was a wet day but apart from the fact that made the track pretty slippery and wet in some places, conditions were good because it was mild," he said.
While it had been cool at the highest point on the Harris Saddle, it was an improvement on previous years when there had been snow on the ground.
"Because of the flow of water in some places we had a number of runners who turned or twisted their ankles, or fell and hurt their hands, but we had plenty of course marshalls dotted the length of the track and everyone except two runners finished," McWhirter said.
