Our "Magnificent Retirement Mutual Funds" list includes some of the best managed and best performing funds around. If you're already invested in these, congratulations! But if you're just now discovering them, don't worry. When it comes to your retirement, it's never too late to start investing in the best.

Great performance, diversification, and low fees: it's a pretty simple formula for a great mutual fund. Some are better than others, but utilizing our Zacks Rank, we have identified three mutual funds that would make great additions to long-term investors' portfolios.

Here are the funds that have achieved the #1 (Strong Buy) Zacks Rank and have low fees.

If you are looking to diversify your portfolio, consider Fidelity Advisor Series Equity Gr (FMFMX Quick QuoteFMFMX - Free Report) . FMFMX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. This fund is a winner, boasting an expense ratio of 0.01%, management fee of 0%, and a five-year annualized return track record of 10.6%.

Janus Henderson Global Technology T (JAGTX Quick QuoteJAGTX - Free Report) . Expense ratio: 0.92%. Management fee: 0.64%. JAGTX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. This fund has managed to produce a robust 16.66% over the last five years.

MSIF International Advantage I (MFAIX Quick QuoteMFAIX - Free Report) . Expense ratio: 0.98%. Management fee: 0.78%. Five year annual return: 10.19%. MFAIX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations.

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.

Do You Know the Top 9 Retirement Investing Mistakes?

Investing in underperforming mutual funds is just one of the key errors that can derail your retirement plans.

To learn more, read our just-released report: 9 Retirement Mistakes You Need to Avoid.