Fullerides are chemical compounds containing fullerene anions. Common fullerides are derivatives of the most common fullerenes, i.e. C₆₀ and C₇₀. The scope of the area is large because multiple charges are possible, i.e., [C₆₀]ⁿ⁻ (n = 1, 2...6), and all fullerenes can be converted to fullerides. The suffix "-ide" implies their negatively charged nature.

Fullerides can be isolated as derivatives with a wide range of cations. Most heavily studied derivatives are those with alkali metals, but fullerides have been prepared with organic cations. Fullerides are typically dark colored solids that generally dissolve in polar organic solvents.

According to electronic structure calculations, the LUMO of C₆₀ is a triply degenerate orbital of t_1u symmetry. Using the technique cyclic voltammetry, C₆₀ can be shown to undergo six reversible reductions starting at −1 V referenced to the Fc⁺/Fc couple. Reduction causes only subtle changes in the structure and many derivatives exhibit disorder, which obscures these effects. Many fullerides are subject to Jahn–Teller distortion. In certain cases, e.g. [PPN]₂C₆₀, the structures are highly ordered and slight (10 pm) elongation of some C−C bonds is observed.

Fullerides have been prepared in various ways:

The fulleride salt ([K(crypt-222)]⁺)₂[C₆₀]²⁻ salt is synthesized by treating C₆₀ with metallic potassium in the presence of [2.2.2]cryptand.

Particular attention has been paid to alkali metal (Na⁺, K⁺, Rb⁺, Cs⁺) derivatives of C₆₀³⁻ because these compounds exhibit physical properties resulting from intercluster interactions such as metallic behavior. In contrast, in C₆₀, the individual molecules interact only weakly, i.e. with essentially nonoverlapping bands. These alkali metal derivatives are sometimes viewed as arising by intercalation of the metal into C₆₀ lattice. Alternatively, these materials are viewed as n-doped fullerenes.

Alkali metal salts of this trianion are superconducting. In M₃C₆₀ (M = Na, K, Rb), the M⁺ ions occupy the interstitial holes in a lattice composed of ccp lattice composed of nearly spherical C₆₀ anions. In Cs₃C₆₀, the cages are arranged in a bcc lattice.

In 1991, it was revealed that potassium-doped C₆₀ becomes superconducting at 18 K (−255 °C). This was the highest transition temperature for a molecular superconductor. Since then, superconductivity has been reported in fullerene doped with various other alkali metals. It has been shown that the superconducting transition temperature in alkaline-metal-doped fullerene increases with the unit-cell volume V. As Cs⁺ is the largest alkali ion, caesium-doped fullerene is an important material in this family. Superconductivity at 38 K (−235 °C) has been reported in bulk Cs₃C₆₀, but only under applied pressure. The highest superconducting transition temperature of 33 K (−240 °C) at ambient pressure is reported for Cs₂RbC₆₀.