| King Alfonso XIII's Cup | |
| Year: | 1928–29 |
| Other Titles: | 29th Copa del Rey |
| Country: | Spain |
| Num Teams: | 32 |
| Defending Champions: | FC Barcelona |
| Winners: | RCD Español |
| Count: | 1 |
| Second: | Real Madrid |
| Matches: | 59 |
| Goals: | 252 |
| Prev Season: | 1928 |
| Next Season: | 1930 |
The King Alfonso XIII's Cup 1928–29 was the 29th staging of the Copa del Rey, the Spanish football cup competition.
The competition started on December 8, 1928, and concluded on February 3, 1929, with the final, held at the Estadio Mestalla in Valencia. RCD Español won the competition for the first time.
32 teams entered the competition, making a new record of participants. Navarre and the Canary Islands sent their champions for the first time. Catalonia, the Centre Region, Gipuzkoa sent three teams each. The rest of communities sent their champions and runners-up.
Iberia SC, Patria Aragón
Real Oviedo, Sporting de Gijón
FC Barcelona, CD Europa, RCD Español
Real Unión, Real Sociedad, CD Logroño
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See main article: article and 1929 Copa del Rey Final.