Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

American Century Heritage A (ATHAX Quick QuoteATHAX - Free Report) has a 1.25% expense ratio and 1% management fee. ATHAX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. With yearly returns of 9.83% over the last five years, this fund clearly wins.

Hartford International Value R5 (HILTX): 0.89% expense ratio and 0.77% management fee. HILTX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets. HILTX, with annual returns of 17.28% over the last five years, is a well-diversified fund with a long track record of success.

Invesco Small Cap Value Y (VSMIX): 0.82% expense ratio and 0.63% management fee. VSMIX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 26.15% over the last five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.