The BAFTA-winning political comedy, starring Peter Capaldi as spin doctor Malcolm Tucker, came to a close with a series low of 753k (3.3%) in BBC Two's 9.30pm slot.
Creator Armando Iannucci confirmed last week that the fourth run would be the show's last. The first two series aired on BBC Four before the corporation promoted it to BBC Two after high viewing figures.
Strictly Come Dancing topped the night with 9.56m (43.5%) in its early 6.30pm slot, maintaining its lead over ITV1's X Factor, which took 8.07m (34.8%) from 8.30pm and 309k (1.5%) on +1.
Before X Factor, Take Me Out rallied to 3.53m (15.5%) at 7.15pm (+1: 175k/0.7%), while Merlin pulled in 5.37m (22.6%) after Strictly.
Elsewhere, Channel 4's film screening of The A-Team attracted 1.7m (8.5%) from 9pm (+1: 429k/3%), and CSI: Miami was Channel 5's best-rated broadcast with 883k (5.1%) at the late time of 10.30pm.
Overall, BBC One scored another convincing primetime victory with 27.8% versus ITV1's 25.4% (+1: 0.9%). Channel 4 edged into third place with 5% (+1: 0.7%), pipping BBC Two's 4.8%, while Channel 5 finished last with 3.3% (+1: 0.1%).
BARB ratings data supplied by Attentional