Novak Djokovic added the 2018 title to his wins in 2011, 2014 and 2015.
Wimbledon Men's Final highlights, Novak Djokovic vs Kevin Anderson Tennis Match: Novak Djokovic became the lowest-ranked champion since Goran Ivanisevic in 2001 to lift the title for the fourth time.
And after a shattering quarter-final exit at this year's Roland Garros, which saw his world ranking slump to its lowest in 12 years, the Serb considered sitting out Wimbledon where he has been champion in 2011, 2014 and 2015.
The 31-year-old former world number one won the last of his 12 majors at the 2016 French Open when he completed the career Grand Slam.
The eagerly-awaited semi-final was halted just after 11pm (2200GMT) under a curfew agreement with Djokovic leading Nadal 6-4, 3-6, 7-6 (11/9).
The epic battle between Kevin Anderson John Isner lasted for 6 hours and 35 minutes with final score reading 7-6, 6-7, 6-7, 6-4, 26-24 in Anderson's favor.
Rafael Nadal will clash against long-time rival Novak Djokovic for the 52nd time on Friday with a Wimbledon 2018 final spot at stake.
Roger Federer suffered one of the most stunning defeats of his career on Wednesday.
Roger Federer blew a two-set lead and wasted a match point in a 2-6, 6-7 (5/7), 7-5, 6-4, 13-11 quarter-final defeat against South Africa's Kevin Anderson.
South Africa's Kevin Anderson moved one step closer to capturing his second consecutive title.
Top seed Marin Cilic from Croatia outplayed Pierre-Hugues Herbert while Kevin Anderson survived a mighty scare from Mikhail Kukushkin.
World number one Nadal defeated South Africa's world number 32 Kevin Anderson 6-3, 6-3, 6-4 in a brutally one-sided final during which he did not face a break point.
Rafael Nadal defeated Argentine 24th seed Juan Martin del Potro 4-6, 6-0, 6-3, 6-2 to book a date in Sunday's final against South African 28th seed Kevin Anderson.
World number one Rafael Nadal powered into his 23rd career Grand Slam final on Friday, routing Argentina's 24th-seeded Juan Martin del Potro.
Yuki Bhambri had stunned Gael Monfils, the defending champion at Citi Open, earlier.
Kevin Anderson has pulled out of the Chennai Open due to a knee injury.
Janko Tipsarevic's inclusion in the 20th edition of the Chennai Open will see 10 players from world's top 50 list.
Kevin Anderson will start the new season in Chennai on the back of a career high top-10 ranking in 2015 and a maiden entry in the men's singles quarter-finals of the US Open after defeating World No.2 Andy Murray of Britain.