Williams, who joined the firm in 2014, will succeed Roger Connon who will step down from the role in April. Connon, who is well-known in boardrooms across Aberdeen, will continue his role as a partner of the firm and will focus on promoting the firm's regulatory compliance business, Cerico, and freelance lawyer service Vario.
Williams is a well-respected figure in the Aberdeen business community and wider oil and gas sector, having advised leading energy and other companies on a range of complex employment issues.
The mother of two has championed the firm's efforts to promote diversity both within and outwith the Pinsent Masons business and combines a successful legal career with a flexible working pattern.
She takes up the role following a period of sustained success for the firm's Aberdeen office. Pinsent Masons moved into new premises on Queens Road in 2013 and recently bought in offshore regulatory specialist Bruce Craig from Mackinnons.
Over the past 12 months the firm has won a number of outstanding mandates in Scotland including advising on the Aberdeen West Peripheral Route, the £410 million Aberdeen Harbour project and acting for Total on its £585 million disposal of the St Fergus gas terminal and North Sea infrastructure.
Pinsent Masons also advised in connection with the landmark £370 million bonds issue by Aberdeen City Council and last month advised on the largest Scottish corporate deal of the year, the £1.4bn sale of Skyscanner.
The Aberdeen office, which includes 10 partners and 25 lawyers, works closely with the firm’s international network of 21 offices including energy-focussed hubs in Dusseldorf, Singapore, Qatar, Melbourne and Dubai.
Earlier this year the firm advised Simmons Private Equity Fund II on the acquisition of LEAP Group in a transaction with aspects in Malaysia, Hong Kong, Australia, Singapore.
John Cleland, managing partner at Pinsent Masons, said: "Aberdeen is a critically important market for us given its position as a true global energy hub, so leadership and a well-executed succession plan is important.
“Roger has done an outstanding job and we were fortunate enough to have a deep pool of talent from which to select a successor. Katie stands out as an individual who is respected massively by our clients. She is a first-class lawyer but also a role model in terms of championing the firm's culture and values."
Katie Williams added: "Roger and the other partners have built an excellent platform in Aberdeen and I am delighted to take over the reins safe in the knowledge that he won't be too far away, which can only smooth the transition.
“Our vision as a firm is to be recognised as an international market leader in the global sectors in which we operate and the energy market in particular is essential to that. We have been bucking the trend in Aberdeen during a period of challenging trading thanks to this focus, our international reach and also our commitment to innovation and efficiency. I look forward driving that forward and building on the fantastic offering developed so far."
Pinsent Masons was last month named Law Firm of the Year at the Legal Week British Legal Awards, replicating success in the Legal Business Awards where it was also named Law Firm of the Year and is ranked in the top five most innovative law firms in Europe by the Financial Times.