"Un-Thinkable (I'm Ready)" is a song by American singer-songwriter Alicia Keys from her fourth studio album The Element of Freedom (2009). It was initially scheduled to be the fifth single, but it was released as the fourth single. It was her first single to reach number one on the R&B chart in the United States since 2007's "Like You'll Never See Me Again"."Un-Thinkable (I'm Ready)" spent twelve consecutive weeks atop the Billboard Hot R&B/Hip-Hop, the longest-running number-one single of 2010, when the single was in its 12th week on top of the chart, Keys has completed a total of 54 weeks at #1 on the chart.

Un-thinkable is a sample of artist Goapele song Closer

"Un-Thinkable (I'm Ready)" is a down-tempo R&B song written by Alicia Keys, Aubrey Graham, Kerry Brothers, Jr., and Noah "40" Shebib in the key of B minor. The vocal range spans from D₃ to D₅ with a moderately slow and simple chord progression of Bm, D major and G major.

Mariel Concepcion from Billboard magazine was positive toward the song noting it as The Element of Freedom's "standout track". Concepcion said "the singer/pianist goes from entertaining puppy love to confessing deeper emotions. Keys sings nervously over extended piano strokes. She finally builds up the courage to share a serious desire with her lover ... atop a building, thumping beat. For an artist who has built her career on songs about love, lust and heartache, Keys has never sounded quite as vulnerable and exposed as she does here." Ashante Infantry from Toronto Star also picked the song as the album's top track saying "Keys is as sexy as she's ever been on the sultry 'Un-Thinkable (I'm Ready)'". Allison Stewart from The Washington Post neither praised nor criticised the song but simple said that Drake's appearance was pointless. "[It fulfills] some sort of unspoken requirement that every female R&B album contain an appearance by at least one cool-but-unthreatening hip-hop star." Molly Lambert from Pitchfork considered the song as the 64th best song of the year saying: "Alicia Keys always puts out one perfect song per album. It's an instant babymaking classic. Skittering beats, trembling synths, deep piano chord progressions, and floating drums. It sounds like it was recorded in a downtempo underwater sex chamber or inside a neon motel sign. It belongs on the Art Laboe Connection forever, with Sade and Minnie Riperton and other sensual heavyweights. It is the eye of the quiet storm".

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