Slavoljub Marjanovic was born on 6 January 1955 in Serbia, then still part of Yugoslavia. He learned to play chess at the age of five and soon had success in various youth tournaments, including international ones.

In 1972 he was a co-winner of the qualifying tournament for the European Under-21 Championship and went on to play in the final. Marjanovic also played in the final of the European Under-21 Championship in 1973 and additionally qualified for the final of the World Under-20 Championship, which at the time was still held as a round-robin tournament. Beliavsky won the event. Marjanovic finished tied for 3rd–5th place with Michael Stean and Larry Christiansen, behind Tony Miles.

At European level, he became co-winner of the B-tournament of the European Under-21 Championship together with Nigel Bloch. At the World Under-20 Championship in 1974 he finished tied for second place behind Tony Miles.

In the following years Marjanovic played in numerous tournaments and was a regular participant in the Yugoslav Championships. In 1985 he won the national title. Among his other successes were tournament victories in Belgrade 1979, Vrnjačka Banja 1982 and Rome 1988. Marjanovic also took part in the Interzonal Tournament in Subotica in 1977, where he finished seventh.   

In 1971, at the age of just 16, he was already part of the Yugoslav team in the match against the USSR, where he played against Petrosian, Beliavsky and Romanishin. Marjanovic was also a member of the Yugoslav team in the matches against the USSR in the following years.

In 1980 he won the bronze medal with the Yugoslav team at the Chess Olympiad in Malta. Marjanovic was again a member of the Yugoslav team at the Chess Olympiad in Thessaloniki in 1984. Between 1977 and 1988 he represented Yugoslavia eight times at the Balkan Championships, winning six team gold medals, one silver and three bronze.

Slavoljub continued to play in team competitions until 2014. His last individual tournament was the Kavala Open in 2012.

Marjanovic was awarded the title of International Master in 1977 and became a Grandmaster in 1978. In 2004 he was named a FIDE Senior Trainer.

Marjanovic passed away last Sunday (8 March 2026). He was 71 years old.