The Chinese company hit a record $1bn (£774m; €883m) in sales in 85 seconds, and then just shy of $10bn in the first hour of the 24-hour spree.
In total, customers spent $30.8bn, up 27% on last year, but the lowest annual increase in the history of Singles Day.
Online discounts have been offered on 11 November, Alibaba's informal holiday for singles, since 2009.
Alibaba Group chief executive Daniel Zhang said the spending bonanza demonstrated "customers' continued pursuit to upgrade their everyday lifestyles".
The event was kicked off on Saturday with a gala featuring US singer Mariah Carey, a Japanese Beyoncé impersonator and a shoe-shopping-themed Cirque du Soleil performance.
What is Singles Day?
Alibaba invented the occasion to celebrate the unattached as an antithesis to the romantically involved on Valentine's Day.
It is now the world's biggest online sales event and this year's total was more than Black Friday and Cyber Monday's totals combined, according to Bloomberg.
Some 180,000 brands are available in the shopping blitz, including top technology companies Xaomi, Apple and Dyson.
Last year, the Chinese company expanded the event to the Western market, with downloads of its app AliExpress surging in the US and UK.
Will Singles Day keep on growing?
The shopping frenzy has broken world records in e-commerce sales - surpassing last year's record at 17:34 Hong Kong Time (10:34 GMT).
However, observers believe as the event matures, its growth rate will slow down.
Alibaba has also faced new challenges this year, such as new rivals in the market, a slowing economy and its stock dropping 16% thanks to China's trade war with the US.
The November sale event is expected to be founder Jack Ma's last at the helm of the company. The current chief executive will take over as chairman next year, Alibaba announced in September.
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