* Q4 net profit 20.8 bln yuan vs 16.9 bln analysts' estimates
* Q4 revenue 66.4 bln yuan vs 69.5 bln expected
* Investments brought in gain of 20.14 bln yuan in 2017
* Games, payment, content and advertising drove growth (Adds details of results)
HONG KONG, March 21 (Reuters) - Chinese internet giant Tencent Holdings Ltd posted a near doubling of quarterly net profit that beat expectations, as it deepened monetisation of its growing customer traffic and its investments paid off following a string of IPOs last year.
Net profit for the three months ended December 31 rose 98 percent to 20.8 billion yuan ($3.29 billion), China's largest social media and gaming company said in a filing to the Hong Kong Stock Exchange.
That was above an average estimate of 16.90 billion yuan from 9 analysts surveyed by Thomson Reuters.
Revenue rose 51 percent to 66.39 billion yuan, below analysts' average estimate of 69.5 billion yuan. Monthly active users of the social media mobile app WeChat exceeded 1 billion after the Chinese New Year in February, up from 980 million at the end of September.
With a market capitalisation of around $560 billion, Tencent is Asia's most valuable listed company and the world's no.5, after Apple Inc, Alphabet Inc, Amazon.com Inc and Microsoft Corp.
Tencent, which derives more than 40 percent of its revenue from games, attributed a 56 percent year-on-year revenue growth for 2017 to games, payment-related services, digital content subscriptions and sales, and social and video advertising.
Tencent said it recorded share of profit of associates and joint ventures of 821 million yuan for the year, compared to a share of losses of 2.52 billion yuan in the previous year. Successful IPOs of its investments, such as Yixin, Netmarble, Sea, ZhongAn Insurance and Sogou, helped it clock other gains totalling 20.14 billion yuan, up from 3.59 billion yuan in the previous year, it said in the filing. ($1 = 6.3304 Chinese yuan renminbi) (Reporting by Sijia Jiang; Editing by Stephen Coates and Muralikumar Anantharaman)