American Century Ultra Fund (AULDX) is a large-cap growth mutual fund managed by American Century Investments that seeks long-term capital appreciation through investments primarily in equity securities of well-established companies exhibiting above-average growth rates, superior profitability, and competitive advantages; the fund maintains a diversified portfolio of 60 to 90 holdings, with approximately 98% allocated to U.S. stocks, emphasizing fundamental research, quality metrics, and risk management to deliver risk-adjusted returns in the large growth category. Core offerings include R6 class shares with a net expense ratio of 0.54%, minimum initial investments waived under certain automatic plans, and daily pricing, benchmarked against the Russell 1000 Growth Index; the fund targets institutional investors, financial advisors, retirement plans, and individual shareholders via intermediaries, with total net assets exceeding $26 billion as of recent reports. American Century Investments, the fund's sponsor founded in 1958 as Twentieth Century Mutual Funds and headquartered at 4500 Main Street in Kansas City, Missouri, operates globally from offices in New York, London, Hong Kong, and Sydney, serving financial professionals, institutions, and individuals through a broad array of mutual funds, ETFs, and retirement solutions. Recent developments at American Century Investments include the September 2023 completion of a strategic transaction acquiring the venture capital team from 3x5 Partners to establish private markets capabilities focused on early-stage growth in healthcare and climate solutions, led by new partners Nicholas Walrod, Tony Arnerich, and Joe Biller reporting to Chief Investment Officer Victor Zhang; this expands offerings for institutional and high-net-worth clients while maintaining operations in Portland, Oregon. Portfolio management saw Tong Li join as co-manager on July 1, 2024, alongside Keith Lee (since 2008) and Jeffrey Bourke (since 2013), supporting low turnover below 20% annually and style-pure large-cap growth positioning amid ongoing fee waivers through July 2026.