How many letters are there in the Spanish alphabet?

29.

As stated on the handbook «Ortografía de la Lengua Española», published by Real Academia Española, the Spanish alphabet stems from the Latin alphabet and was constituted in 1803. It has a total of 29 letters ‘“ 26 of them are common to other Latin-based alphabets, and 3 of them are specific to the Spanish language: ch, ll and ñ.