Sikka, 47, will replace S D Shibulal, one of the seven engineers who founded Infosys in 1981, from August 1, Infosys said in a statement.
Also, the firm's Executive Chairman N R Narayana Murthy and Executive Vice Chairman S Gopalakrishnan will step down on June 14. Murthy will be designated as chairman emeritus from October 11.
Sikka, who will also be the company's MD, quit SAP in May. He comes in at a time when Infosys has had four straight years of narrowing margins. Besides, almost a dozen senior executives have left since last year when co-founder Murthy returned as chairman.
Infosys said the chairman's office would be dissolved and Rohan would leave the company on Saturday, when the company will hold its annual shareholders meeting in Bangalore.
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A Stanford University computer science Ph.D graduate, Sikka oversaw the development of new products, including a platform for quickly analysing large databases as the chief technology officer at SAP, the world's largest maker of business-management software.
His appointment brings down the curtain on a year of suspense, which saw an 11 senior level exists since June last year, when Murthy was brought back from retirement to head the company and put it back on a high-growth trajectory at a time when peers like TCS and HCL Tech were out-performing Infosys.
The Infosys scrip was down 0.19 per cent on the BSE in the afternoon trade.