Guaimar I (also Waimar, Gaimar, or Guaimario) (c. 855 – 901) was the prince of Salerno from 880, when his father entered the monastery of Monte Cassino in August.
From 877, he was associated with his father on the throne, a practice which had begun with the previous dynasty and continued until the end of Salernitan independence in 1078.
Besides Saracens, Guaimar also had to fight the duke-bishop Athanasius of Naples, who was ruling over Capua, technically a Salernitan vassal.
In 886, he travelled with Lando II of Capua to Constantinople and did homage, returning in 887 with the title of patrician from the emperor.
It is not certain whether Guaimar accepted, but he tried to assassinate the gastald of Avellino, Adelferio, and was taken prisoner with his wife whatever the case.