It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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.

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

Fidelity OTC Portfolio (FOCPX Quick QuoteFOCPX - Free Report) has a 0.81% expense ratio and 0.68% management fee. FOCPX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With yearly returns of 10.92% over the last five years, this fund clearly wins.

Neuberger Berman Guardian Institutional (NGDLX Quick QuoteNGDLX - Free Report) . Expense ratio: 0.68%. Management fee: 0.63%. NGDLX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. This fund has managed to produce a robust 10.72% over the last five years.

T. Rowe Price Health Sciences (PRHSX Quick QuotePRHSX - Free Report) : 0.8% expense ratio and 0.63% management fee. PRHSX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy. With a five-year annual return of 11.08%, 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.