McLanachan (34), an apprentice gardener, won his first Otago senior men's track title at the Caledonian Ground in 33min 8.20sec.
He was followed home by Jonah Smith (Caversham), 34min 58.12sec and Kerrin Williams (Hill City-University), 35min 12.81sec.
''I'm stoked,'' McLanachan said.
''I've been after the title for over 10 years and I've finally knocked it off.''
He finished second to Tom Hunt (Hill City) five years ago and has been third on two other occasions.
McLanachan started too fast and blew up when he lost to Hunt. He was more cautious on Saturday and lapped a steady 78sec and 79sec for the first eight laps, reaching halfway in 16min 20sec.
The pace was too hot for Smith, who was dropped in the third of 25 laps.
McLanachan was by himself from that point, winning by a massive 1min 58sec.
''It was a mental battle with myself after that,'' he said.
The only other major senior race won by McLanachan was the Edmond Cup steeplechase at Wingatui during the harrier season, nearly six years ago.
Smith won the junior men's title and Williams the masters event.
Shauna Pali (Hill City-University) was the first woman home in 40min 39.17sec and Maria Sleeman (Caversham) won the women's over-50 section in 42min 59.18sec.
Barbara Patrick (Hill City) was second in 46min 36.27sec and broke the New Zealand masters over-65 record by 1min 21sec.
It was the second New Zealand record broken by Patrick this season. She set a new 3km mark of 13min 29.37sec at the South Island championships in Nelson two weeks ago.
New Zealand junior representative Rebekah Greene (Hill City-University) had her first outing on the track this summer, finishing second in the junior women's 200m in 28.05sec. She was the first woman home in the 400m in 59.08sec.
Greene intends to run in the 800m, 1500m and mile in the New Zealand classic series next month.
Liz Wilson (Hill City-University) broke the masters women's 400m Otago record with her time of 64.19sec.
Claire Giles (Caversham) broke the masters women's aged 55 to 59 200m record with a time of 31.33sec.
The other records came in the pole vault.
Ian Craven (Hill City-University) jumped 2.60m to improve his masters men's aged 55 to 59 Otago record by 15cm. Daughter Rosie Craven equalled her own Otago women's aged 15 pole vault record with 2.50m.