UK /ˌʌn.rɪˈkwaɪ.tɪd/, US /ˌʌn.rɪˈkwaɪ.t̬ɪd/. Four syllables, main stress on -quit-, lighter stress on un. Say it: un-ri-KWY-tid.
US only: the middle t flaps softly, as in cutting. UK keeps a clear t.
How your mouth makes it
Say un with your tongue resting low-mid and central in your mouth, the same shape as the vowel in cup. Barely drop your jaw, and keep the sound quick and unstressed.
Glide from r straight into KWY: start the k at the back of your tongue, round your lips as the w follows, then stretch into the long ai sound. This syllable carries the main stress, so give it your strongest beat.
End with tid: tap your tongue tip once behind your top teeth for the t. In the US variety, let that tap be soft and quick, like the middle sound of cutting. In the UK, keep it a crisp, clear t.
Say it in a phrase
Say it in a short phrase: her unrequited love or an unrequited love. Keep the strong beat on -quit- so the rhythm stays even when the phrase speeds up.
Keep the middle ri audible: a common shorter version is un-KWY-tid, with only three syllables, while the target is un-ri-KWY-tid, four syllables with the beat on KWY.
A frequent learner version squeezes it to three, as un-KWY-tid, which drops the middle ri. Say both and keep all four syllables.
Contrast with stress placement: say UN-ri-kwy-tid, with the beat on un.
Now say the target, un-ri-KWY-tid, with the beat on KWY. Cambridge marks main stress on -quit- and lighter stress on un, so practise both aloud and hear which matches that pattern.
Self-check: say an unrequited love three times, keeping KWY loudest each time. If any syllable disappears, slow down and count un, ri, kwy, tid as you say it.