Most acidic citrus fruit is

The most acidic citrus fruit is Citrus megalaxycarpa.
Citrus has had a significant role in dietary and medicinal purposes from time immemorial and is widely acknowledged for its therapeutic properties. Citric acid is found naturally in citrus fruits, especially lemons and limes.
Citrus megaloxycarpa Lush. is a little-known sibling of the genus Citrus and family Rutaceae with an unknown origin. Large, vigorous, open-growing trees. Leaves are large, citron-like in appearance. Fruits look like medium to medium/large citron. Rind yellow, rough, medium thick.