Bill Ackman's Pershing Square fund has allocated approximately 15% of its portfolio to Microsoft, a stake valued at $2.4 billion. Ackman believes the market undervalues Microsoft's AI strategy and its 27% stake in OpenAI (which he estimates could be independently valued at up to $200 billion), despite Microsoft's plan to invest approximately $190 billion in AI and cloud infrastructure by 2026. Pershing Square began building its position in Microsoft in February 2026.