IS/1 was the world's first

relational database A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relatio ...

system, implemented at the IBM United Kingdom Scientific Centre in Peterlee in the years 1970–1972.Notley, M, "Peterlee IS/1 System", UKSC Report 18, 1972 It had limited facilities but implemented a true relational model. It was the precursor to PRTV.

References

IS1 Relational database management systems {{database-software-stub