Bongmusa Mthembu also won his maiden title in the men's race, after clinching the 'down run' title by a comfortable margin.
However, in one of the biggest reversals ever witnessed in the history of the race, Greenwood came from being close to eight minutes behind with around 18 kilometres remaining, to win in a time of six hours, 18 minutes and 15 seconds (6:18.15).
That gave the 35-year-old a handsome five minute and four second victory over legendary Russian Elena Nurgalieva (6:23.18), who was bidding to win a record ninth crown and equal the mark held by Bruce Fordyce.
Twin sister Olesya, a double former champion, came third in a time of a 6:24.51.
In the men's race, Nedbank runner Mthembu, winner of three previous gold medals in one of the world's most famous ultra marathons, crossed the line in a time of 5:28.34.
He finished the 89.28 kilometres race over four minutes ahead of Ludwick Mamabolo, the defending 'down run' winner from 2012 who recorded a time of 5:33.14.
Mthembu took the lead just before Cowies Hill -- approximately 17 kilometres before the Kingsmead Stadium finish -- and never looked back, finishing strongly on his way to claiming the R350,000 top-prize.
Gift Kelehe, brother of 2001 winner Andrew, came third in a time of 5:34.39 with three-time former champion Stephen Muzhingi (5:35.18) of Zimbabwe fourth, followed by another South African Rufus Photo (5:35.30) in fifth.
Results from the 2014 Comrades Marathon women's race run from Pietermaritzburg to Durban on Sunday:
1. Eleanor Greenwood (Nedbank RC) GREAT BRITAIN six hours, 18 minutes and 15 seconds (6:18:15)
2. Elena Nurgalieva (Toyota AC) RUSSIA 6:23:18
3. Olesya Nurgalieva (Toyota AC) RUSSIA 6:24:51
4. Irina Antropova (Nedbank RC) RSA 6:34:08
5. Jo Meek (Toyota AC) GREAT BRITAIN 6:47:02
6. Caroline Wostmann (Nedbank RC) GAUTENG 6:51:43
7. Zola Budd Pieterse (Hooters AC) RSA 6:55:55
8. Frida Sdermark (GoIF Tjalve) SWEDEN 6:57:33
9. Martinique Potgieter (Pietersburg RR) LIMPOPO 7:00:46
10. Julanie Basson (Toyota AC) GAUTENG 7:02:50
Results from the 2014 Comrades Marathon men's race run from Pietermaritzburg to Durban on Sunday:
1. Bongmusa Mthembu (Nedbank RC) KZN 5:28:34
2. Ludwick Mamabolo (Nedbank RC) GAUTENG 5:33:14
3. Gift Kelehe (Samancor Chrome MC) LIMPOPO 5:34:39
4. Stephen Muzhingi (Toyota AC) ZIMBABWE 5:35:18
5. Rufus Photo (Pietersburg RR) LIMPOPO 5:35:30
6. Mncedisi Mkhize (Maxed Elite) KZN 5:36:06
7. Jonas Buud (Nedbank RC) SWEDEN 5:38:17
8. Manoko William Mokwalakwala GAUTENG 5:39:29
9. Prodigal Khumalo (Maxed Elite) ZIMBABWE 5:39:36
10. Latudi Makofane (Samancor CM) Limpopo 5:40:41
<strong>SEND US YOUR PICS!</strong> Send your Comrades Marathon photos to <a href="mailto:firstname.lastname@example.org"> <strong>Sport24</strong></a> to be included in our Comrades Marathon gallery!