Kenjutsu (剣術), which predates modern kendo, is the art of using the Japanese sword.
Kenjutsu usually refers to the methods or techniques of swordsmanship of traditional schools, called Koryū (古流), i.e. Japanese martial art schools that were founded before 1868 (Meiji restoration).
Although Kendō (剣道, lit. “The way of the sword” also called “Ken no michi”) can be used to indicate Japanese swordsmanship in general, these days it is most often used for what can be called “Shinai-kendō” (modern kendo using bamboo swords, called “shinai”, and protective gear).
Ono Ha Ittō Ryū (小野 派 一刀 流) is one of the most influential traditional Kenjutsu styles in Japan.
More information on traditional Japanese schools can be found in the next article: Traditional Kenjutsu Schools