What a priceless goal this could be for the home team as it reduced Celtic's lead at the top of the table to four points with the Gers still having two games in hand.
The noise from the Ibrox crowd was as loud as any top European night and even manager Walter Smith became involved when four minutes were added to normal time, mainly because of Motherwell's earlier time-wasting.
Rangers started brightly and David Weir flicked on a Steven Davis corner, only for keeper Graeme Smith to touch his header onto the bar. Nacho Novo reached the rebound first but pulled his shot wide.
Motherwell then came more and more into the game with Bob Malcolm pulling the strings as he was left unmarked in the middle of the pitch.
Ross McCormack flashed over a dangerous cross before Carlos Cuellar dispossessed the Motherwell striker after Steven Whittaker had carelessly given away possession.
The visitors wasted their best chance of the half when, from six yards, McCormack shot wide from Stephen Hughes' cutback.
Rangers nearly took the lead just before half-time but Jean-Claude Darcheville's shot found the side-netting after good work by Kris Boyd.
At the start of the second half Rangers surged forward with wave after wave of attacks. Twice Boyd headed over from good positions.
Ferguson's pass put Darcheville through but the striker widely slashed his effort over the bar.
Kevin Thomson's deflected shot reached Novo in the six-yard box but he was crowded out before he could shoot.
Motherwell could hardly get over the halfway line and it was no surprise when Rangers' pressure finally paid off. Another Davis corner was touched on at the near post and, from beyond the back post, Ferguson shot high into the net from an acute angle.
Rangers went after a second and had a good claim for a penalty turned down when Malcolm pushed Boyd in the back, but the home team gained the three points they so desperately needed.