Poly(phenazine-2,7-diyl), P(2,7-Phzn), a new pi-conjugated polymer constituted of highly electron-accepting phenazine units, has been prepared by dehalogenation polymerization of 2,7-dibromophenazine. The polymer undergoes electrochemical reduction with E-p of -1.45 V versus Ag\Ag+, and the potential is the highest amongst reported reduction potentials of poly(arylene)s. Oligomeric poly(thianthrene-2,7-diyl), an analogue of P(2,7-Phzn), is also electrochemically active.