Julio César Villalba Gaona (born 17 September 1998) is a Paraguayan professional footballer who plays as a forward for Ecuadorian club Guayaquil City.

Villalba signed with Borussia Mönchengladbach in January 2017.^[2]

Upon returning to Paraguay, he featured for Cerro Porteño U20 in the 2016 U-20 Copa Libertadores.^[3][4][5]

He made his first-team debuts for Cerro Porteño during 2016 and the club will enjoy little of him before the player departs permanently to the Bundesliga.^[6]

On 8 January 2020, Villalba was sent on loan to SC Rheindorf Altach of the Austrian Bundesliga for the remainder of the season.^[7]

Villalba featured in Cerro Porteno's youth academy and Paraguay U17 alongside Sergio Díaz.

Villalba played at the 2015 South American Under-17 Football Championship, making 8 appearances.^{[8][9][10][11][12][13][14][15]}

He then featured at the 2015 FIFA U-17 World Cup making three appearances and scoring two goals against Syria U17^[16] and France U17.^[17][18]