The video debuted on MTV in the US and the entertainer's official website on Thursday night.
Beyoncé offers a nod to Audrey Hepburn in the '60s-inspired clip, appearing in a series of pop-art and op-art inspired outfits. She teams a large black and white striped hat with a variety of brightly coloured leotards, and is also seen with a hairdo similar to that of Holly Golightly, Hepburn's character in Breakfast at Tiffany's.
A later scene bears some parallels to Alex Owens's (Jennifer Beals) audition scene in the original Flashdance movie as the singer performs an energetic dance routine in a large studio space.
'Countdown' is the third single from the multi-million-selling album 4, following 'Run the World (Girls)' and 'Best Thing I Never Had'. Written and produced by a team including Beyoncé herself, it features a sample from Boyz II Men's 1991 hit 'Uhh Ahh'.
In August, the 30-year-old singer announced that she is expecting her first child with husband Jay-Z. She has described her pregnancy as "an incredible gift", insisting that she is "the happiest [she has] ever been".
It appears that Beyoncé may have shot different parts of the 'Countdown' video at different stages of her pregnancy, as her baby bump is showing more in some shots than in others.
Beyoncé revealed recently that being pregnant has made her nose especially sensitive, saying that she hates her husband's fragrance now that she is expecting a child.
The singer first released a 30-second snippet of the new music video earlier this week.