Or do you?
While "Chinese" is generally accepted as implying the ability to communicate in Standard 普通话 (Mandarin Chinese), "Chinese" does in fact refer not only to Mandarin but to a whole group of languages and dialects from across China, Hong Kong and Taiwan.
While it is almost impossible to say exactly how many dialects are still in regular use, the dialects can be roughly split into seven larger groups;
-普通话 Pǔtōnghuà (Mandarin Chinese)
-吴语 Wúyǔ (Wu Chinese)
-粤语 Yuèyǔ (Cantonese)
-闽南语 Mǐnnányǔ (South Fujianese Dialects)
-客家话 Kèjiāhuà (Hakka)
-湘语 Xiāngyǔ (Hunanese)
-赣语 Gànyǔ (Gan)
Each of these groups encompasses a number of 方言 (fāngyán: regional dialects) which I'll be touching on later in this collection.
In the meantime, next time you declare yourself a Chinese speaker, it might be worth indicating which kind of Chinese you speak...!