Late last week, two of music's biggest stars dropped new singles, both of which saw explosive viewership numbers within hours of their release.

Over three years after her most-recent upload, Adele released the video for her new single "Hello" in the early hours of Friday morning (approximately 12amPT). Within 48 hours, it had been viewed 50 million times, making it the biggest debut of any video on YouTube in 2015 and one of the most-watched music video debuts of all time.

In fact, "adele hello" was, by far, YouTube's top search on Friday and Saturday, and the video garnered as much as 1.6 million views in a single hour, averaging over 1 million views per hour over the first two days.

(For comparison, the release of the massively anticipated full trailer for "Star Wars Episode VII: The Force Awakens" peaked at 1.2 million views per hour.)

Meanwhile, Justin Bieber scored another massive debut -- third-largest music video debut of 2015 -- and did so... without being in the video. The release -- designated as a "dance video" -- for the song "Sorry" was seen approximately 20 million times in its first 48 hours.

Both releases also helped grow these artists' respective YouTube audiences considerably as well, with Adele gaining over 400,000 subscribers over the weekend and Bieber picking up over 150,000 in the three days following his new vid.

If you're one of the handful of people who have missed these two premieres, you can see them both below.

-- Kevin Allocca