French forward Saha was released by Sunderland last month meaning he is able to sign outside of a transfer window.
Lazio said in a statement the 34-year-old former Manchester United front-man would be presented at a news conference later.
The Rome club, who have reached the Italian Cup final and lie in the third and final Champions League spot in Serie A, were rocked earlier this week by news top-scorer Klose would be out for as much as eight weeks with a knee injury.
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