RadioTimes.com voted for the scene from the Cornwall-set drama, where Ross Poldark - played by Aidan Turner - is bathed by wife Demelza, portrayed by Eleanor Tomlinson.
Turner takes the prize for a second year running, following his topless scything scene from series one in 2015.
More than 2,000 people took part in the online poll.
They were asked to choose from a shortlist of 35 clips said to be among the most dramatic, inspiring and emotional TV moments of the year.
RadioTimes.com's biggest TV moments of 2016
1. Aidan Turner in a tin bath (Poldark)
2. The Shelbys are arrested (Peaky Blinders)
3. Tom Hiddleston bares all (The Night Manager)
4. Ross and Elizabeth's controversial bedroom scene (Poldark)
5. Snake attack on baby iguanas (Planet Earth II)
6. Hodor holds the door (Game of Thrones)
7. Ed Balls does Gangnam Style (Strictly Come Dancing)
8. The Brownlee brothers go arm-in-arm to the finish line (Triathlon World Series)
9. Jon Snow is resurrected (Game of Thrones)
10. Andrei and Natasha waltz at the ball (War and Peace)
The moment in Peaky Blinders when the Shelbys were arrested was voted the second biggest moment of the past 12 months, followed by Tom Hiddleston's brief flash of nudity in the Night Manager.
Poldark also featured at number four in the list, for a controversial scene in which Ross Poldark pushed former fiancee Elizabeth onto a bed after she rejected his advances.
The top five was rounded off by a clip from Sir David Attenborough's Planet Earth II in which baby iguanas were seen being chased by snakes.
Former shadow chancellor Ed Balls also made the list, for his dance to Psy's Gangnam Style on Strictly Come Dancing.
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A steamy bath scene from the second series of Poldark has topped a poll of the biggest television moments of 2016.