The new six-part series starring Keeley Hawes and Richard Madden debuted on Sunday night at 9pm to an average overnight rating of 6.7 million and an audience share of 35%, the BBC said.
The programme peaked with 6.9 million viewers.
The second most-watched new drama launch of the year so far is BBC One’s McMafia, which had an average overnight audience of 5.6m when it aired on New Year’s Day, while ITV dramas Innocent and Girlfriends opened with 5.3 million and 5.2 million average viewers respectively.
Bodyguard was also the most-watched broadcast of Sunday night, ahead of the News at 10pm on BBC One, which had an average audience of 5.1 million.
The series, penned by Line Of Duty writer Jed Mercurio, sees Ashes To Ashes star Hawes play fictional home secretary Julia Montague while Game Of Thrones actor Madden is the bodyguard assigned to protect her.
The dramatic first instalment focused on an attempted bombing on a London train.
Viewers were highly entertained by the political thriller’s first episode, with some taking to Twitter to say they were gripped and could not wait for the second episode.
“Opening twenty minutes most tense drama this year,” wrote one viewer on Twitter.
“Richard Madden is immense and Keeley Hawes is as excellent as ever.”
Another posted: “#Bodyguard was brilliant!! omg literally on the edge of my seat!!
“OMG that opening scene, what?!?! My heart can’t take that much tension!!”
Episode two of Bodyguard airs on Monday at 9pm.