A unified treatment of injection and mutual phase locking phenomena in microwave oscillators coupled by a network characterized by a Y-matrix is presented. Under certain simplifying assumptions, steady state solutions such as locking frequency and oscillation phase relation are given with emphasis placed on the coupling-network dependence of locking bandwidth. Also, some examples of locking system specified by y(21)=0, Y(21)= Y(12) and y21= -Y12 are briefly discussed.