Intersection of two or more silicon slot waveguides is inevitable in modern optical integrated circuits based on a silicon-on-insulator platform. We design a Maxwell’s fisheye lens as the crossing medium for three Si slot waveguides and numerically investigate its characteristics, such as insertion loss, cross talk, and bandwidth. For the 3  ×  3 slot waveguide crossing, the average insertion loss of 1.2 dB and cross talk levels lower than −15.1  dB are achieved in an ultrawideband wavelength range of 415 nm covering the entire O, E, S, C, L, and U bands of optical communications. The footprint of the 3  ×  3 silicon slot waveguide crossing presented in our paper is merely 2  ×  2  μm², which is considerably smaller compared to the previously designed Si slot waveguide crossings even with fewer ports. The proposed design can be expanded to support the intersection of more slot waveguides.