Organism that lives inside of plants, often to the benefit of the plant.

Endophytes typically are fungi though instead can be bacteria. The benefit they bestow, giving rise to mutualisms between endophyte and plant, can be due to resistance to pathogenic microorganisms, interference with , or enhancing plant tolerance to additional ecological phenomena including abiotic factors.

Among fungi, endophytes often are ascomycetes.

Endophytes can vary in terms of whether they are versus between plants, in terms of what plants they are capable of associating with (i.e., host range), in terms of what sorts of organisms they are (e.g., bacteria, fungi, even other plants), in terms of how physiologically or ecologically they affect plants, as well as in terms of the degree to which they are or are not helpful to plants.