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.

Guinness Atkinson Global Innovators Fund (IWIRX Quick QuoteIWIRX - Free Report) : 1.24% expense ratio and 0.75% management fee. IWIRX 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. IWIRX has achieved five-year annual returns of an astounding 15.87%.

Janus Henderson Research I (JRAIX Quick QuoteJRAIX - Free Report) : 0.57% expense ratio and 0.48% management fee. JRAIX 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. JRAIX, with annual returns of 16.54% over the last five years, is a well-diversified fund with a long track record of success.

T. Rowe Price Diversified Mid-Cap Growth (PRDMX Quick QuotePRDMX - Free Report) . Expense ratio: 0.86%. Management fee: 0.64%. Five year annual return: 11.85%. PRDMX is a Mid Cap Growth mutual fund. Mid Cap Growth funds pick stocks--usually companies with a market cap between $2 billion and $10 billion--that demonstrate extensive growth opportunities for investors compared to their peers.

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.