To get from Lagos in Portugal to Seville in Spain you need to take the bus. You can purchase tickets from the bus station which is opposite the marina, or online on the Rede Expressos website. You can’t buy tickets on-board, so make sure you buy them a day or so in advance or give yorself plenty of time on the day to queue and buy a ticket. The bus station is open Monday to Saturday 06h15 – 20h30 and Sundays 07h15 – 20h30. Be prepared for the bus to be full in peak season. A one way ticket is €20 and a return ticket is €34.
The bus between Lagos and Seville is operated jointly by Eva Bus (Portugal) and DAMAS (Spain). If you want to book for the opposite direction (Seville to Lagos) then book on the DAMAS website or at the bus station in Seville. The journey takes around 5 and a half hours.
There are several bus stations in Seville- buses to and from Lagos operate out of Plaza de Armas.