Lychee is a tropical tree that bears fleshy fruits of the same name that is native to China. The Lychee is part of the soapberry family and its fruit is enclosed in a reddish shell, with a whiteish pink transparent flesh that carries a seed in the middle. Lychee fruits can be eaten on their own or can be used to make a number of different desserts.
The correct pronunciation of lychee is disputed, and as a consequence there are three common variations: Lie-chee, Lee-chee and Lit-chee.
You'll be surprised to hear that all three variations are correct in English. The reason for this is due to the fact that each pronunciation is derived from a different language, one from Cantonese, one from Mandarin and one from Latin.
In British English, Lie-chee, is the most common way that lychee is pronounced. This derives from Cantonese, where the "Ly" is pronounced as -Lie.
In American English, it is most common to hear lychee pronounced as Lee-chee. Lee-chee actually derives from the Mandarin pronunciation of lychee, where the "Ly" is pronounced as -Lee.
The third pronunciation of lychee, Lit-chee, which is slightly less common than the previous two, actually derives from the Latin name for the species, which is Litchi Chinensis.
This is one of those rare cases where all the different variations of lychee in English are perfectly acceptable and there is no univocally correct answer.