A novel single-negative magnetic waveguided metamaterial (MTM) is initially proposed based on the Hilbert-shaped complementary electric inductive-capacitive resonator. The MTM element is highly compact due to the Hilbert space-filling curves which considerably enhance the current path in the ground, and exhibits a bandgap attributing to the negative permeability in the vicinity of magnetic resonance. Taking the advantage of these two features, a microstrip antenna array is then designed, fabricated, and measured by embedding a 5×1 array of the well-engineered MTM elements between two closely spaced (λo/8.08) H-plane coupled rectangular patches. Both numerical and experimental results indicate a mutual coupling reduction of more than 9.7 dB. The proposed prescription with electrically small dimensions and high decoupling efficiency opens an avenue to new types of antennas with super performances.