the effective medium regime, known for its tolerance to small-scale geometry variations. [9][10][11][12][13] We present comprehensive theoretical, experimental, and numerical analysis of the electromagnetic properties of the magneto-optical metamaterial, demonstrating both the rotation of the polarization plane and nonreciprocal transmission, two phenomena that can be controlled by the direction of the external magnetic field. This enhanced response is the result of the combination of the introduced magneto-optical properties and strong anisotropy of the metamaterial. We demonstrate rotation of the polarization plane with the effective Verdet constant equivalent of at least 10 5 rad m −1 T −1 , significant enhancement with respect to bulk ferromagnetic materials, [14] suggesting that nanostructured magnetic materials have much stronger magneto-optical response than their bulk counterparts. Overall, plasmonic magneto-optical nanorods combine the benefits of sub-wavelength light manipulation offered by metamaterials and of strong magneto-optics offered by plasmonic nanocomposites, leading to a promising material platform for integrated nanophotonic applications.The magneto-optical metamaterial geometry and its optical response are illustrated in Figure 1. The composite is formed by an array of aligned plasmonic (gold) nanorods with magnetooptical (nickel) shells inside a dielectric (alumina) matrix (note that in the composites the Ni shells extend only part-way along the rod; see the Experimental Section). As follows from the geometry, in the absence of an external static magnetic field and in the limit when the unit cell is much smaller than the wavelength (a << λ 0 ), the optical response of the composite can be described by a diagonal permittivity tensor with Cartesian components = ⊥ ⊥ zẑ { , , } . Effective medium theory can be used to relate the components of the effective permittivity ⊥ and zz to the permittivity of the constituent materials as well as to the geometrical parameters of a metamaterial, such as a unit cell a, and radii of the rod r 1 and of the shells around the rod r i , with i = 2, …, N. Existing analytical and numerical tools allow calculations of the optical response of metamaterials composed of rods without shells, with plasmonic and magneto-optical material constituents and in the limit r 1 << a, [1,11,13,15] as well as shelled nanorod composites, comprising nonmagneto-optical materials with arbitrary rod concentration. [12,16] Here, we present a formalism that can incorporate magneto-optical response in the effective-medium description of shelled rod metamaterials and even in the limit r a i 2 . We consider a metamaterial with a = 64 nm, r 1 = 15 nm, and r 2 = 23 nm and assume that the Magneto-optical effects are at the heart of modern technologies providing opportunities for polarization control in laser physics and optical communications, metrology, and in high-density data storage. Here a new type of a hyperbolic magneto-optical metamaterial based on Au-Ni nanorod arrays ...