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.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Baron Fifth Avenue Growth Institutional (BFTIX Quick QuoteBFTIX - Free Report) : 0.75% expense ratio and 0.7% management fee. BFTIX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With annual returns of 18.19% over the last five years, this fund is a winner.

Franklin DynaTech R (FDNRX Quick QuoteFDNRX - Free Report) . Expense ratio: 1.08%. Management fee: 0.46%. FDNRX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. This fund has managed to produce a robust 19.16% over the last five years.

Dreyfus Appreciation Fund Y (DGYGX Quick QuoteDGYGX - Free Report) : 0.59% expense ratio and 0.55% management fee. DGYGX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With a five-year annual return of 11.59%, this fund is a well-diversified fund with a long track record of success.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.

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.