Millwall manager Nigel Spackman has signed former Coventry City veteran Richard Shaw.
The former Crystal Palace man arrives at The Den after being released by The Sky Blues at the end of the season.
The defender brings a wealth of experience to The Lions, having made over 350 senior appearances during his career.
He is joined at The Den by former Tottenham keeper Chris Day, who arrives from League One rivals Oldham Athletic.
The 30-year-old has signed a two-year deal with the South East London club after making 30 appearances for The Latics last term.
"I had a few options at the end of the season and spoke to a few interested clubs, but once I spoke to Nigel, I knew that Millwall was where I wanted to play next year," Day told The Stellar Group's official website.
"Although the club struggled last year, there is a really positive atmosphere from what I've seen of the place so far and everyone is desperate to get back into The Championship next year."
Day will contest the number one jersey with fellow summer signing Lenny Pidgeley, who also arrived this summer from Premiership champions Chelsea.
Meanwhile, Lions defender Mark Phillips has signed a new two-year contract with the club.