In this chapter, we treat circular data as unit complex numbers and model their correlation by multiplying them in the complex plane. We propose a general complex multiplication framework for circular regression. The proposed framework is very flexible in the sense that several different models can be included as special cases. Based on the linear relationship, a linear complex multiplication model is introduced and discussed in detail. Our estimation and inference results are presented together with a simulation study and two real data examples and are compared with those of two existing methods.