San Marino participated in the Eurovision Song Contest 2018, held in Lisbon, Portugal. The Sammarinese national broadcaster Radiotelevisione della Repubblica di San Marino (SMRTV) partnered with the London-based company 1in360 to stage an online search for their entrant, marking the first time the nation did not select their representative internally. The process, entitled 1in360, culminated in an 11-participant final with acts chosen from three wildcard selection processes and two 11-act showcase events. The winner of 1in360 was "Who We Are" performed by Jessika featuring Jenifer Brening. The 2018 entry in the Eurovision Song Contest was promoted through performances in London, Amsterdam, Madrid and Lisbon as well as a 10-week anti-bullying campaign to raise money for the Diana Award. San Marino performed fourth in the second semi-final, held on 10 May 2018, and placed 17th with 28 points, failing to qualify for the final.

The Eurovision Song Contest 2018 was the 63rd edition of the Eurovision Song Contest. It took place in Lisbon, Portugal, following the country's victory at the 2017 contest with the song "Amar pelos dois" by Salvador Sobral. Organised by the European Broadcasting Union (EBU) and host broadcaster Rádio e Televisão de Portugal (RTP), the contest was held at the Lisbon Arena, and consisted of two semi-finals on 8 and 10 May, and a final on 12 May 2018. The three live shows were presented by Portuguese television presenters Filomena Cautela, Sílvia Alberto and Catarina Furtado, and Portuguese-American actress Daniela Ruah, marking the first time that the contest was presented by four hosts.