The acquisition, which The Wall Street Journal said could be announced Wednesday, would combine two of the largest U.S. drugstore chains. Rite Aid shares soared after the news, closing Tuesday more than 40 percent higher.
Before the spike Tuesday, Rite Aid had a market capitalization of about $6.4 billion. The deal could value Rite Aid at about $10 billion, according to the Journal.
Walgreens shares rose about 4 percent after the report.
The acquisition would come amid a wave of consolidation in the health care sector. Among other proposals this year, Aetna offered about $37 billion for Humana, and Centene bid $6.3 billion for Health Net.
Many companies in the industry have looked to cut costs in recent years amid changes like the Affordable Care Act.
Walgreens had net sales of $76.4 billion in fiscal 2014, accounting for about 20 percent of the retail prescription drug market. Rite Aid had prescription drug sales of $18.1 billion in fiscal 2015, up from $17.2 billion in the previous year.
Shares of drugstore chain CVS also rose about 1 percent Tuesday after the report.
Walgreens Boots Alliance declined to comment to CNBC. Rite Aid did not immediately respond to CNBC's request to comment.