Little is known of the early life of Claudius's third wife, Valeria Messalina, although she was a well-connected member of the imperial family. They married in 37 or 38CE when she was between 17 and 20 years old (not as young as 15 as some authors state although this may not have been her first marriage) and Claudius was 48. There has been some suggestion that her second-cousin, the Emperor Gaius (Caligula) arranged the marriage as a joke. At that time, Claudius was considered an embarrassment to the imperial family due to his stutter and tremor.
Claudius unexpectedly became emperor in 41 after Gaius was murdered. Messalina, who already held sway over her weak husband, became the most influencial woman in Rome. Claudius indulged her every whim and erected statues in her honour around the city. Insecure about her position, though, Messalina brought about the deaths of many of her opponents and when this failed, she could usually persuade her husband to exile those who she perceived to be a threat to her or her young son and successor to Claudius's throne, Britannicus.
However, it is as an adulteress that Messalina is known today. She never had the political skill of Claudius's second wife, Agrippina and ultimately failed to appreciate the limits of her influence over Claudius.
In 47, Messalina began an affair with Gaius Silius. Claudius was typically happy to turn a blind eye to his young wife's exploits but when she and Silius conducted a public wedding ceremony, Claudius was forced to take action in fear that the two were plotting his assassination. Messalina was sentenced to death and, unable to take her own life, was stabbed to death by one of Claudius's officers.