Skysports.com understands Per Mertesacker has passed a medical and agreed personal terms with Arsenal.
The giant Werder Bremen centre-back is in London ahead of what is reportedly a £10million transfer on a three-year contract.
Arsenal boss Arsene Wenger turned his attention to Mertesacker, who has entered the final year of his contract in Germany, after deciding Bolton's Gary Cahill was too expensive.
The move comes in the wake of Sunday's 8-2 humiliation at Manchester United, which convinced Wenger of the need to strengthen his defence.
Mertesacker, 26, has already made 75 appearances for Germany and will therefore bring vast experience with him to Emirates Stadium.
Arsenal are also on the brink of signing Brazilian left-back Andre Santos in a £6m move from Fenerbahce ahead of Wednesday's transfer deadline.
Earlier on Tuesday, the Premier League club confirmed the signing of South Korea international striker Park Chu-young from Monaco.