In this paper, a novel low complexity energy efficient recon-figurable reduced dimension maximum likelihood (RRDML) multiple-input multiple-output (MIMO) detector is proposed. RRDML is based on RDML [1], in which maximum likelihood (ML) is applied to detect a sub-dimension of the received vector and linear detection is used for the remaining dimension. The channel condition number is employed to configure RRDML. For a 4×4 MIMO system with 16-QAM modulation over a Rayleigh fading channel, Verilog simulation in a commercial 45nm, 1.2V CMOS process show that RRDML achieves up to 62.3% power savings with a BER loss at most 3.7% compared to ML based receivers.