(Reuters) - Elliott Investment Management has built an over $2.5 billion stake in U.S. oil refiner Phillips 66, a person familiar with the matter said on Monday, days after the activist investor took a stake in London-listed oil major BP.

American Paul Elliott Singer's hedge fund firm was established in 1977 and is known as being one of the most vocal activists. Elliott managed around $69.7 billion in assets as of June 30, 2024, its website says.

Here are some of Elliott's top activist campaigns against U.S and European companies. The hedge fund declined to comment on its investments.

Honeywell

** Investment first disclosed: November 2024

** Changes asked: Break-up of conglomerate structure

** Changes made: Honeywell to split into three independently listed companies

Anglo American

** Investment first disclosed: April 2024, after the London-listed miner became a takeover target by bigger rival BHP Group ( BHP )

** Changes asked: Elliott has yet to publicly comment on its Anglo investment

Southwest Airlines ( LUV )

** Investment first disclosed: June 2024

** Changes asked: Replacement of some board members, improvement of financial and share price performance, CEO ouster

** Changes made: The airline added five Elliott nominees to its board, making it the most seats the hedge fund has ever gotten in a settlement with a company in the U.S. The deal allowed CEO Bob Jordan to retain his job

Starbucks ( SBUX )

** Investment first disclosed: July 2024

** Changes asked: Proposed board expansion and governance improvement

** Changes made: Starbucks ( SBUX ) last year named Chipotle Mexican Grill ( CMG ) head Brian Niccol as its new CEO, though Elliott was not demanding a CEO change

Aspen Technology ( AZPN )

** Investment first disclosed: February 2025

** Changes asked: Opposing the company's decision to accept Emerson Electric's ( EMR ) $7.2 billion tender offer

Akzo Nobel

** Investment first disclosed: 2017

** Changes asked: Akzo to negotiate a potential sale to U.S. coatings manufacturer PPG Industries Inc ( PPG )

** Changes made: Akzo and Elliott Advisors ended a dispute after the activist investor agreed to halt legal action against the Dutch paint company

** Elliott agreed to support the nomination of new CEO and two supervisory board members. Akzo promised to give Elliott and other major shareholders a say in naming a third supervisory board member

BHP

** Investment first disclosed: 2017

** Changes asked: Called for the company to sell off its oil business and ditch its dual listing structure

** Changes made: BHP exited the oil business in 2021

Phillips 66

** Investment first disclosed: November 2023

** Changes asked: Elliott criticized Phillips 66's refining operations and asked the U.S. oil refiner to overhaul its board to boost performance

** Changes made (as of 2024): Disposed assets worth $3 billion, added new director to the board with Elliott's approval