Let E/Q be an elliptic curve with complex multiplication (CM), and for each prime p of good reduction, let a E (p) = p + 1 − #E(F p ) denote the trace of Frobenius. By theIn this paper, we prove that the least prime p such thatwhere N E is the conductor of E and the implied constant and exponent A > 2 are absolute and effectively computable. Our result is an analogue for CM elliptic curves of Linnik's Theorem for arithmetic progressions, which states that the least prime p ≡ a (mod q) for (a, q) = 1 satisfies p q L for an absolute constant L > 0.